--- a/browser/components/extensions/test/browser/.eslintrc.js
+++ b/browser/components/extensions/test/browser/.eslintrc.js
@@ -24,13 +24,9 @@ module.exports = {  // eslint-disable-li
     "closeContextMenu": true,
     "closeExtensionContextMenu": true,
     "focusWindow": true,
     "makeWidgetId": true,
     "openContextMenu": true,
     "openExtensionContextMenu": true,
     "CustomizableUI": true,
   },
-
-  "rules": {
-    "no-shadow": 0,
-  },
 };

--- a/browser/components/extensions/test/browser/browser_ext_browserAction_context.js
+++ b/browser/components/extensions/test/browser/browser_ext_browserAction_context.js
@@ -1,31 +1,45 @@
 /* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
 /* vim: set sts=2 sw=2 et tw=80: */
 "use strict";
 
 function* runTests(options) {
   function background(getTests) {
-    async function checkDetails(expecting, tabId) {
-      let title = await browser.browserAction.getTitle({tabId});
-      browser.test.assertEq(expecting.title, title,
-                            "expected value from getTitle");
-
-      let popup = await browser.browserAction.getPopup({tabId});
-      browser.test.assertEq(expecting.popup, popup,
-                            "expected value from getPopup");
+    // Gets the current details of the browser action, and returns a
+    // promise that resolves to an object containing them.
+    function getDetails(tabId) {
+      return Promise.all([
+        browser.browserAction.getTitle({tabId}),
+        browser.browserAction.getPopup({tabId}),
+        browser.browserAction.getBadgeText({tabId}),
+        browser.browserAction.getBadgeBackgroundColor({tabId})]
+      ).then(details => {
+        return Promise.resolve({title: details[0],
+                                popup: details[1],
+                                badge: details[2],
+                                badgeBackgroundColor: details[3]});
+      });
+    }
 
-      let badge = await browser.browserAction.getBadgeText({tabId});
-      browser.test.assertEq(expecting.badge, badge,
-                            "expected value from getBadge");
+    function checkDetails(expecting, tabId) {
+      return getDetails(tabId).then(details => {
+        browser.test.assertEq(expecting.title, details.title,
+                              "expected value from getTitle");
+
+        browser.test.assertEq(expecting.popup, details.popup,
+                              "expected value from getPopup");
 
-      let badgeBackgroundColor = await browser.browserAction.getBadgeBackgroundColor({tabId});
-      browser.test.assertEq(String(expecting.badgeBackgroundColor),
-                            String(badgeBackgroundColor),
-                            "expected value from getBadgeBackgroundColor");
+        browser.test.assertEq(expecting.badge, details.badge,
+                              "expected value from getBadge");
+
+        browser.test.assertEq(String(expecting.badgeBackgroundColor),
+                              String(details.badgeBackgroundColor),
+                              "expected value from getBadgeBackgroundColor");
+      });
     }
 
     let expectDefaults = expecting => {
       return checkDetails(expecting);
     };
 
     let tabs = [];
     let tests = getTests(tabs, expectDefaults);
@@ -59,25 +73,28 @@ function* runTests(options) {
       }
     }
 
     // Runs the next test in the `tests` array, checks the results,
     // and passes control back to the outer test scope.
     function nextTest() {
       let test = tests.shift();
 
-      test(async expecting => {
+      test(expecting => {
         // Check that the API returns the expected values, and then
         // run the next test.
-        let tabs = await browser.tabs.query({active: true, currentWindow: true});
-        await checkDetails(expecting, tabs[0].id);
-
-        // Check that the actual icon has the expected values, then
-        // run the next test.
-        browser.test.sendMessage("nextTest", expecting, tests.length);
+        new Promise(resolve => {
+          return browser.tabs.query({active: true, currentWindow: true}, resolve);
+        }).then(tabs => {
+          return checkDetails(expecting, tabs[0].id);
+        }).then(() => {
+          // Check that the actual icon has the expected values, then
+          // run the next test.
+          browser.test.sendMessage("nextTest", expecting, tests.length);
+        });
       });
     }
 
     browser.test.onMessage.addListener((msg) => {
       if (msg != "runNextTest") {
         browser.test.fail("Expecting 'runNextTest' message");
       }
 
@@ -219,110 +236,117 @@ add_task(function* testTabSwitchContext(
         {"icon": browser.runtime.getURL("default-2.png"),
          "popup": browser.runtime.getURL("default-2.html"),
          "title": "Default Title 2",
          "badge": "d2",
          "badgeBackgroundColor": [0, 0xff, 0, 0xff]},
       ];
 
       return [
-        async expect => {
+        expect => {
           browser.test.log("Initial state, expect default properties.");
-
-          await expectDefaults(details[0]);
-          expect(details[0]);
+          expectDefaults(details[0]).then(() => {
+            expect(details[0]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Change the icon in the current tab. Expect default properties excluding the icon.");
           browser.browserAction.setIcon({tabId: tabs[0], path: "1.png"});
-
-          await expectDefaults(details[0]);
-          expect(details[1]);
+          expectDefaults(details[0]).then(() => {
+            expect(details[1]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Create a new tab. Expect default properties.");
-          let tab = await browser.tabs.create({active: true, url: "about:blank?0"});
-          tabs.push(tab.id);
-
-          await expectDefaults(details[0]);
-          expect(details[0]);
+          browser.tabs.create({active: true, url: "about:blank?0"}, tab => {
+            tabs.push(tab.id);
+            expectDefaults(details[0]).then(() => {
+              expect(details[0]);
+            });
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Change properties. Expect new properties.");
           let tabId = tabs[1];
           browser.browserAction.setIcon({tabId, path: "2.png"});
           browser.browserAction.setPopup({tabId, popup: "2.html"});
           browser.browserAction.setTitle({tabId, title: "Title 2"});
           browser.browserAction.setBadgeText({tabId, text: "2"});
           browser.browserAction.setBadgeBackgroundColor({tabId, color: "#ff0000"});
           browser.browserAction.disable(tabId);
 
-          await expectDefaults(details[0]);
-          expect(details[2]);
+          expectDefaults(details[0]).then(() => {
+            expect(details[2]);
+          });
         },
         expect => {
           browser.test.log("Navigate to a new page. Expect no changes.");
 
           // TODO: This listener should not be necessary, but the |tabs.update|
           // callback currently fires too early in e10s windows.
           browser.tabs.onUpdated.addListener(function listener(tabId, changed) {
             if (tabId == tabs[1] && changed.url) {
               browser.tabs.onUpdated.removeListener(listener);
               expect(details[2]);
             }
           });
 
           browser.tabs.update(tabs[1], {url: "about:blank?1"});
         },
-        async expect => {
+        expect => {
           browser.test.log("Switch back to the first tab. Expect previously set properties.");
-          await browser.tabs.update(tabs[0], {active: true});
-          expect(details[1]);
+          browser.tabs.update(tabs[0], {active: true}, () => {
+            expect(details[1]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Change default values, expect those changes reflected.");
           browser.browserAction.setIcon({path: "default-2.png"});
           browser.browserAction.setPopup({popup: "default-2.html"});
           browser.browserAction.setTitle({title: "Default Title 2"});
           browser.browserAction.setBadgeText({text: "d2"});
           browser.browserAction.setBadgeBackgroundColor({color: [0, 0xff, 0, 0xff]});
           browser.browserAction.disable();
-
-          await expectDefaults(details[3]);
-          expect(details[3]);
+          expectDefaults(details[3]).then(() => {
+            expect(details[3]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Re-enable by default. Expect enabled.");
           browser.browserAction.enable();
-
-          await expectDefaults(details[4]);
-          expect(details[4]);
+          expectDefaults(details[4]).then(() => {
+            expect(details[4]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Switch back to tab 2. Expect former value, unaffected by changes to defaults in previous step.");
-          await browser.tabs.update(tabs[1], {active: true});
-
-          await expectDefaults(details[3]);
-          expect(details[2]);
+          browser.tabs.update(tabs[1], {active: true}, () => {
+            expectDefaults(details[3]).then(() => {
+              expect(details[2]);
+            });
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Delete tab, switch back to tab 1. Expect previous results again.");
-          await browser.tabs.remove(tabs[1]);
-          expect(details[4]);
+          browser.tabs.remove(tabs[1], () => {
+            expect(details[4]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Create a new tab. Expect new default properties.");
-          let tab = await browser.tabs.create({active: true, url: "about:blank?2"});
-          tabs.push(tab.id);
-          expect(details[5]);
+          browser.tabs.create({active: true, url: "about:blank?2"}, tab => {
+            tabs.push(tab.id);
+            expect(details[5]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Delete tab.");
-          await browser.tabs.remove(tabs[2]);
-          expect(details[4]);
+          browser.tabs.remove(tabs[2], () => {
+            expect(details[4]);
+          });
         },
       ];
     },
   });
 });
 
 add_task(function* testDefaultTitle() {
   yield runTests({
@@ -362,46 +386,46 @@ add_task(function* testDefaultTitle() {
         {"title": "",
          "popup": "",
          "badge": "",
          "badgeBackgroundColor": DEFAULT_BADGE_COLOR,
          "icon": browser.runtime.getURL("icon.png")},
       ];
 
       return [
-        async expect => {
+        expect => {
           browser.test.log("Initial state. Expect extension title as default title.");
-
-          await expectDefaults(details[0]);
-          expect(details[0]);
+          expectDefaults(details[0]).then(() => {
+            expect(details[0]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Change the title. Expect new title.");
           browser.browserAction.setTitle({tabId: tabs[0], title: "Foo Title"});
-
-          await expectDefaults(details[0]);
-          expect(details[1]);
+          expectDefaults(details[0]).then(() => {
+            expect(details[1]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Change the default. Expect same properties.");
           browser.browserAction.setTitle({title: "Bar Title"});
-
-          await expectDefaults(details[2]);
-          expect(details[1]);
+          expectDefaults(details[2]).then(() => {
+            expect(details[1]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Clear the title. Expect new default title.");
           browser.browserAction.setTitle({tabId: tabs[0], title: ""});
-
-          await expectDefaults(details[2]);
-          expect(details[2]);
+          expectDefaults(details[2]).then(() => {
+            expect(details[2]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Set default title to null string. Expect null string from API, extension title in UI.");
           browser.browserAction.setTitle({title: ""});
-
-          await expectDefaults(details[3]);
-          expect(details[3]);
+          expectDefaults(details[3]).then(() => {
+            expect(details[3]);
+          });
         },
       ];
     },
   });
 });

--- a/browser/components/extensions/test/browser/browser_ext_incognito_popup.js
+++ b/browser/components/extensions/test/browser/browser_ext_incognito_popup.js
@@ -9,92 +9,91 @@ add_task(function* testIncognitoPopup() 
       "browser_action": {
         "default_popup": "popup.html",
       },
       "page_action": {
         "default_popup": "popup.html",
       },
     },
 
-    background: async function() {
+    background() {
       let resolveMessage;
       browser.runtime.onMessage.addListener(msg => {
         if (resolveMessage && msg.message == "popup-details") {
           resolveMessage(msg);
         }
       });
 
       let awaitPopup = windowId => {
         return new Promise(resolve => {
           resolveMessage = resolve;
         }).then(msg => {
           browser.test.assertEq(windowId, msg.windowId, "Got popup message from correct window");
           return msg;
         });
       };
 
-      let testWindow = async window => {
-        let [tab] = await browser.tabs.query({active: true, windowId: window.id});
-
-        await browser.pageAction.show(tab.id);
-        browser.test.sendMessage("click-pageAction");
+      let testWindow = window => {
+        return browser.tabs.query({active: true, windowId: window.id}).then(([tab]) => {
+          return browser.pageAction.show(tab.id);
+        }).then(() => {
+          browser.test.sendMessage("click-pageAction");
 
-        let msg = await awaitPopup(window.id);
-        browser.test.assertEq(window.incognito, msg.incognito, "Correct incognito status in pageAction popup");
+          return awaitPopup(window.id);
+        }).then(msg => {
+          browser.test.assertEq(window.incognito, msg.incognito, "Correct incognito status in pageAction popup");
 
-        browser.test.sendMessage("click-browserAction");
+          browser.test.sendMessage("click-browserAction");
 
-        msg = await awaitPopup(window.id);
-        browser.test.assertEq(window.incognito, msg.incognito, "Correct incognito status in browserAction popup");
+          return awaitPopup(window.id);
+        }).then(msg => {
+          browser.test.assertEq(window.incognito, msg.incognito, "Correct incognito status in browserAction popup");
+        });
       };
 
       const URL = "http://example.com/incognito";
       let windowReady = new Promise(resolve => {
         browser.tabs.onUpdated.addListener(function listener(tabId, changed, tab) {
           if (changed.status == "complete" && tab.url == URL) {
             browser.tabs.onUpdated.removeListener(listener);
             resolve();
           }
         });
       });
 
-      try {
-        {
-          let window = await browser.windows.getCurrent();
-
-          await testWindow(window);
-        }
-
-        {
-          let window = await browser.windows.create({incognito: true, url: URL});
-          await windowReady;
-
-          await testWindow(window);
-
-          await browser.windows.remove(window.id);
-        }
-
+      browser.windows.getCurrent().then(window => {
+        return testWindow(window);
+      }).then(() => {
+        return browser.windows.create({incognito: true, url: URL});
+      }).then(window => {
+        return windowReady.then(() => {
+          return testWindow(window);
+        }).then(() => {
+          return browser.windows.remove(window.id);
+        });
+      }).then(() => {
         browser.test.notifyPass("incognito");
-      } catch (error) {
+      }).catch(error => {
         browser.test.fail(`Error: ${error} :: ${error.stack}`);
         browser.test.notifyFail("incognito");
-      }
+      });
     },
 
     files: {
       "popup.html": '<html><head><meta charset="utf-8"><script src="popup.js"></script></head></html>',
 
-      "popup.js": async function() {
-        let win = await browser.windows.getCurrent();
-        browser.runtime.sendMessage({
-          message: "popup-details",
-          windowId: win.id,
-          incognito: browser.extension.inIncognitoContext,
+      "popup.js": function() {
+        browser.windows.getCurrent().then(win => {
+          browser.runtime.sendMessage({
+            message: "popup-details",
+            windowId: win.id,
+            incognito: browser.extension.inIncognitoContext,
+          });
+          window.close();
         });
-        window.close();
       },
     },
   });
 
   extension.onMessage("click-browserAction", () => {
     clickBrowserAction(extension, Services.wm.getMostRecentWindow("navigator:browser"));
   });
 

--- a/browser/components/extensions/test/browser/browser_ext_legacy_extension_context_contentscript.js
+++ b/browser/components/extensions/test/browser/browser_ext_legacy_extension_context_contentscript.js
@@ -22,29 +22,27 @@ function promiseAddonStartup(extension) 
  * tab info.
  */
 add_task(function* test_legacy_extension_context_contentscript_connection() {
   function backgroundScript() {
     // Extract the assigned uuid from the background page url and send it
     // in a test message.
     let uuid = window.location.hostname;
 
-    browser.test.onMessage.addListener(async msg => {
+    browser.test.onMessage.addListener(msg => {
       if (msg == "open-test-tab") {
-        let tab = await browser.tabs.create({url: "http://example.com/"});
-        browser.test.sendMessage("get-expected-sender-info",
-                                 {uuid, tab});
+        browser.tabs.create({url: "http://example.com/"})
+          .then(tab => browser.test.sendMessage("get-expected-sender-info", {
+            uuid, tab,
+          }));
       } else if (msg == "close-current-tab") {
-        try {
-          let [tab] = await browser.tabs.query({active: true});
-          await browser.tabs.remove(tab.id);
-          browser.test.sendMessage("current-tab-closed", true);
-        } catch (e) {
-          browser.test.sendMessage("current-tab-closed", false);
-        }
+        browser.tabs.query({active: true})
+          .then(tabs => browser.tabs.remove(tabs[0].id))
+          .then(() => browser.test.sendMessage("current-tab-closed", true))
+          .catch(() => browser.test.sendMessage("current-tab-closed", false));
       }
     });
 
     browser.test.sendMessage("ready");
   }
 
   function contentScript() {
     browser.runtime.sendMessage("webextension -> legacy_extension message", (reply) => {

--- a/browser/components/extensions/test/browser/browser_ext_optionsPage_privileges.js
+++ b/browser/components/extensions/test/browser/browser_ext_optionsPage_privileges.js
@@ -12,27 +12,26 @@ add_task(function* test_tab_options_priv
           browser.test.log(`Error: ${error} :: ${error.stack}`);
           browser.test.notifyFail("options-ui-privileges");
         });
       }
     });
     browser.runtime.openOptionsPage();
   }
 
-  async function optionsScript() {
-    try {
-      let [tab] = await browser.tabs.query({url: "http://example.com/"});
-      browser.test.assertEq("http://example.com/", tab.url, "Got the expect tab");
-
-      tab = await browser.tabs.getCurrent();
+  function optionsScript() {
+    browser.tabs.query({url: "http://example.com/"}).then(tabs => {
+      browser.test.assertEq("http://example.com/", tabs[0].url, "Got the expect tab");
+      return browser.tabs.getCurrent();
+    }).then(tab => {
       browser.runtime.sendMessage({msgName: "removeTabId", tabId: tab.id});
-    } catch (error) {
+    }).catch(error => {
       browser.test.log(`Error: ${error} :: ${error.stack}`);
       browser.test.notifyFail("options-ui-privileges");
-    }
+    });
   }
 
   const ID = "options_privileges@tests.mozilla.org";
   let extension = ExtensionTestUtils.loadExtension({
     useAddonManager: "temporary",
 
     manifest: {
       applications: {gecko: {id: ID}},

--- a/browser/components/extensions/test/browser/browser_ext_pageAction_context.js
+++ b/browser/components/extensions/test/browser/browser_ext_pageAction_context.js
@@ -74,105 +74,108 @@ add_task(function* testTabSwitchContext(
           browser.tabs.onUpdated.addListener(function listener(tabId, changed) {
             if (tabId == details.id && changed.url == details.url) {
               browser.tabs.onUpdated.removeListener(listener);
               resolve();
             }
           });
         });
       };
-
       return [
         expect => {
           browser.test.log("Initial state. No icon visible.");
           expect(null);
         },
-        async expect => {
+        expect => {
           browser.test.log("Show the icon on the first tab, expect default properties.");
-          await browser.pageAction.show(tabs[0]);
-          expect(details[0]);
+          browser.pageAction.show(tabs[0]).then(() => {
+            expect(details[0]);
+          });
         },
         expect => {
           browser.test.log("Change the icon. Expect default properties excluding the icon.");
           browser.pageAction.setIcon({tabId: tabs[0], path: "1.png"});
           expect(details[1]);
         },
-        async expect => {
+        expect => {
           browser.test.log("Create a new tab. No icon visible.");
-          let tab = await browser.tabs.create({active: true, url: "about:blank?0"});
-          tabs.push(tab.id);
-          expect(null);
+          browser.tabs.create({active: true, url: "about:blank?0"}, tab => {
+            tabs.push(tab.id);
+            expect(null);
+          });
         },
         expect => {
           browser.test.log("Await tab load. No icon visible.");
           expect(null);
         },
-        async expect => {
+        expect => {
           browser.test.log("Change properties. Expect new properties.");
           let tabId = tabs[1];
-          await browser.pageAction.show(tabId);
+          browser.pageAction.show(tabId).then(() => {
+            browser.pageAction.setIcon({tabId, path: "2.png"});
+            browser.pageAction.setPopup({tabId, popup: "2.html"});
+            browser.pageAction.setTitle({tabId, title: "Title 2"});
 
-          browser.pageAction.setIcon({tabId, path: "2.png"});
-          browser.pageAction.setPopup({tabId, popup: "2.html"});
-          browser.pageAction.setTitle({tabId, title: "Title 2"});
-
-          expect(details[2]);
+            expect(details[2]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Change the hash. Expect same properties.");
 
-          let promise = promiseTabLoad({id: tabs[1], url: "about:blank?0#ref"});
+          promiseTabLoad({id: tabs[1], url: "about:blank?0#ref"}).then(() => {
+            expect(details[2]);
+          });
+
           browser.tabs.update(tabs[1], {url: "about:blank?0#ref"});
-          await promise;
-
-          expect(details[2]);
         },
         expect => {
           browser.test.log("Clear the title. Expect default title.");
           browser.pageAction.setTitle({tabId: tabs[1], title: ""});
 
           expect(details[3]);
         },
-        async expect => {
+        expect => {
           browser.test.log("Navigate to a new page. Expect icon hidden.");
 
           // TODO: This listener should not be necessary, but the |tabs.update|
           // callback currently fires too early in e10s windows.
-          let promise = promiseTabLoad({id: tabs[1], url: "about:blank?1"});
+          promiseTabLoad({id: tabs[1], url: "about:blank?1"}).then(() => {
+            expect(null);
+          });
 
           browser.tabs.update(tabs[1], {url: "about:blank?1"});
-
-          await promise;
-          expect(null);
         },
-        async expect => {
+        expect => {
           browser.test.log("Show the icon. Expect default properties again.");
-
-          await browser.pageAction.show(tabs[1]);
-          expect(details[0]);
+          browser.pageAction.show(tabs[1]).then(() => {
+            expect(details[0]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Switch back to the first tab. Expect previously set properties.");
-          await browser.tabs.update(tabs[0], {active: true});
-          expect(details[1]);
+          browser.tabs.update(tabs[0], {active: true}, () => {
+            expect(details[1]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Hide the icon on tab 2. Switch back, expect hidden.");
-          await browser.pageAction.hide(tabs[1]);
-
-          await browser.tabs.update(tabs[1], {active: true});
-          expect(null);
+          browser.pageAction.hide(tabs[1]).then(() => {
+            browser.tabs.update(tabs[1], {active: true}, () => {
+              expect(null);
+            });
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Switch back to tab 1. Expect previous results again.");
-          await browser.tabs.remove(tabs[1]);
-          expect(details[1]);
+          browser.tabs.remove(tabs[1], () => {
+            expect(details[1]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Hide the icon. Expect hidden.");
-
-          await browser.pageAction.hide(tabs[0]);
-          expect(null);
+          browser.pageAction.hide(tabs[0]).then(() => {
+            expect(null);
+          });
         },
       ];
     },
   });
 });

--- a/browser/components/extensions/test/browser/browser_ext_pageAction_popup.js
+++ b/browser/components/extensions/test/browser/browser_ext_pageAction_popup.js
@@ -34,17 +34,17 @@ add_task(function* testPageActionPopup()
 
       "data/popup-b.html": scriptPage("popup-b.js"),
       "data/popup-b.js": function() {
         browser.runtime.sendMessage("from-popup-b");
       },
 
       "data/background.html": scriptPage("background.js"),
 
-      "data/background.js": async function() {
+      "data/background.js": function() {
         let tabId;
 
         let sendClick;
         let tests = [
           () => {
             sendClick({expectEvent: false, expectPopup: "a"});
           },
           () => {
@@ -110,17 +110,17 @@ add_task(function* testPageActionPopup()
           } else {
             browser.test.fail("unexpected click event");
           }
 
           expect.event = false;
           browser.test.sendMessage("next-test");
         });
 
-        browser.test.onMessage.addListener(msg => {
+        browser.test.onMessage.addListener((msg) => {
           if (msg == "close-popup") {
             browser.runtime.sendMessage("close-popup");
             return;
           }
 
           if (msg != "next-test") {
             browser.test.fail("Expecting 'next-test' message");
           }
@@ -128,21 +128,23 @@ add_task(function* testPageActionPopup()
           if (tests.length) {
             let test = tests.shift();
             test();
           } else {
             browser.test.notifyPass("pageaction-tests-done");
           }
         });
 
-        let [tab] = await browser.tabs.query({active: true, currentWindow: true});
-        tabId = tab.id;
+        browser.tabs.query({active: true, currentWindow: true}, tabs => {
+          tabId = tabs[0].id;
 
-        await browser.pageAction.show(tabId);
-        browser.test.sendMessage("next-test");
+          browser.pageAction.show(tabId).then(() => {
+            browser.test.sendMessage("next-test");
+          });
+        });
       },
     },
   });
 
   extension.onMessage("send-click", () => {
     clickPageAction(extension);
   });
 

--- a/browser/components/extensions/test/browser/browser_ext_pageAction_title.js
+++ b/browser/components/extensions/test/browser/browser_ext_pageAction_title.js
@@ -79,100 +79,106 @@ add_task(function* testTabSwitchContext(
           });
         });
       };
       return [
         expect => {
           browser.test.log("Initial state. No icon visible.");
           expect(null);
         },
-        async expect => {
+        expect => {
           browser.test.log("Show the icon on the first tab, expect default properties.");
-          await browser.pageAction.show(tabs[0]);
-          expect(details[0]);
+          browser.pageAction.show(tabs[0]).then(() => {
+            expect(details[0]);
+          });
         },
         expect => {
           browser.test.log("Change the icon. Expect default properties excluding the icon.");
           browser.pageAction.setIcon({tabId: tabs[0], path: "1.png"});
           expect(details[1]);
         },
-        async expect => {
+        expect => {
           browser.test.log("Create a new tab. No icon visible.");
-          let tab = await browser.tabs.create({active: true, url: "about:blank?0"});
-          tabs.push(tab.id);
-          expect(null);
+          browser.tabs.create({active: true, url: "about:blank?0"}, tab => {
+            tabs.push(tab.id);
+            expect(null);
+          });
         },
         expect => {
           browser.test.log("Await tab load. No icon visible.");
           expect(null);
         },
-        async expect => {
+        expect => {
           browser.test.log("Change properties. Expect new properties.");
           let tabId = tabs[1];
+          browser.pageAction.show(tabId).then(() => {
+            browser.pageAction.setIcon({tabId, path: "2.png"});
+            browser.pageAction.setPopup({tabId, popup: "2.html"});
+            browser.pageAction.setTitle({tabId, title: "Title 2"});
 
-          await browser.pageAction.show(tabId);
-          browser.pageAction.setIcon({tabId, path: "2.png"});
-          browser.pageAction.setPopup({tabId, popup: "2.html"});
-          browser.pageAction.setTitle({tabId, title: "Title 2"});
-
-          expect(details[2]);
+            expect(details[2]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Change the hash. Expect same properties.");
 
-          let promise = promiseTabLoad({id: tabs[1], url: "about:blank?0#ref"});
+          promiseTabLoad({id: tabs[1], url: "about:blank?0#ref"}).then(() => {
+            expect(details[2]);
+          });
 
           browser.tabs.update(tabs[1], {url: "about:blank?0#ref"});
-
-          await promise;
-          expect(details[2]);
         },
         expect => {
           browser.test.log("Clear the title. Expect default title.");
           browser.pageAction.setTitle({tabId: tabs[1], title: ""});
 
           expect(details[3]);
         },
-        async expect => {
+        expect => {
           browser.test.log("Navigate to a new page. Expect icon hidden.");
 
           // TODO: This listener should not be necessary, but the |tabs.update|
           // callback currently fires too early in e10s windows.
-          let promise = promiseTabLoad({id: tabs[1], url: "about:blank?1"});
+          promiseTabLoad({id: tabs[1], url: "about:blank?1"}).then(() => {
+            expect(null);
+          });
 
           browser.tabs.update(tabs[1], {url: "about:blank?1"});
-
-          await promise;
-          expect(null);
         },
-        async expect => {
+        expect => {
           browser.test.log("Show the icon. Expect default properties again.");
-          await browser.pageAction.show(tabs[1]);
-          expect(details[0]);
+          browser.pageAction.show(tabs[1]).then(() => {
+            expect(details[0]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Switch back to the first tab. Expect previously set properties.");
-          await browser.tabs.update(tabs[0], {active: true});
-          expect(details[1]);
+          browser.tabs.update(tabs[0], {active: true}, () => {
+            expect(details[1]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Hide the icon on tab 2. Switch back, expect hidden.");
-          await browser.pageAction.hide(tabs[1]);
-          await browser.tabs.update(tabs[1], {active: true});
-          expect(null);
+          browser.pageAction.hide(tabs[1]).then(() => {
+            browser.tabs.update(tabs[1], {active: true}, () => {
+              expect(null);
+            });
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Switch back to tab 1. Expect previous results again.");
-          await browser.tabs.remove(tabs[1]);
-          expect(details[1]);
+          browser.tabs.remove(tabs[1], () => {
+            expect(details[1]);
+          });
         },
-        async expect => {
+        expect => {
           browser.test.log("Hide the icon. Expect hidden.");
-          await browser.pageAction.hide(tabs[0]);
-          expect(null);
+          browser.pageAction.hide(tabs[0]).then(() => {
+            expect(null);
+          });
         },
       ];
     },
   });
 });
 
 add_task(function* testDefaultTitle() {
   yield runTests({
@@ -200,20 +206,21 @@ add_task(function* testDefaultTitle() {
          "icon": browser.runtime.getURL("icon.png")},
       ];
 
       return [
         expect => {
           browser.test.log("Initial state. No icon visible.");
           expect(null);
         },
-        async expect => {
+        expect => {
           browser.test.log("Show the icon on the first tab, expect extension title as default title.");
-          await browser.pageAction.show(tabs[0]);
-          expect(details[0]);
+          browser.pageAction.show(tabs[0]).then(() => {
+            expect(details[0]);
+          });
         },
         expect => {
           browser.test.log("Change the title. Expect new title.");
           browser.pageAction.setTitle({tabId: tabs[0], title: "Foo Title"});
           expect(details[1]);
         },
         expect => {
           browser.test.log("Clear the title. Expect extension title.");

--- a/browser/components/extensions/test/browser/browser_ext_popup_shutdown.js
+++ b/browser/components/extensions/test/browser/browser_ext_popup_shutdown.js
@@ -1,18 +1,19 @@
 /* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
 /* vim: set sts=2 sw=2 et tw=80: */
 "use strict";
 
 let getExtension = () => {
   return ExtensionTestUtils.loadExtension({
-    background: async function() {
-      let [tab] = await browser.tabs.query({active: true, currentWindow: true});
-      await browser.pageAction.show(tab.id);
-      browser.test.sendMessage("pageAction ready");
+    background() {
+      browser.tabs.query({active: true, currentWindow: true}, tabs => {
+        browser.pageAction.show(tabs[0].id)
+          .then(() => { browser.test.sendMessage("pageAction ready"); });
+      });
     },
 
     manifest: {
       "browser_action": {
         "default_popup": "popup.html",
         "browser_style": false,
       },
 

--- a/browser/components/extensions/test/browser/browser_ext_runtime_openOptionsPage.js
+++ b/browser/components/extensions/test/browser/browser_ext_runtime_openOptionsPage.js
@@ -56,17 +56,17 @@ add_tasks(function* test_inline_options(
   let extension = yield loadExtension(Object.assign({}, extraOptions, {
     manifest: {
       applications: {gecko: {id: "inline_options@tests.mozilla.org"}},
       "options_ui": {
         "page": "options.html",
       },
     },
 
-    background: async function() {
+    background: function() {
       let _optionsPromise;
       let awaitOptions = () => {
         browser.test.assertFalse(_optionsPromise, "Should not be awaiting options already");
 
         return new Promise(resolve => {
           _optionsPromise = {resolve};
         });
       };
@@ -77,73 +77,76 @@ add_tasks(function* test_inline_options(
             _optionsPromise.resolve(sender.tab);
             _optionsPromise = null;
           } else {
             browser.test.fail("Saw unexpected options page load");
           }
         }
       });
 
-      try {
-        let [firstTab] = await browser.tabs.query({currentWindow: true, active: true});
+      let firstTab, optionsTab;
+      browser.tabs.query({currentWindow: true, active: true}).then(tabs => {
+        firstTab = tabs[0].id;
 
         browser.test.log("Open options page. Expect fresh load.");
-
-        let [, optionsTab] = await Promise.all([
+        return Promise.all([
           browser.runtime.openOptionsPage(),
           awaitOptions(),
         ]);
+      }).then(([, tab]) => {
+        browser.test.assertEq("about:addons", tab.url, "Tab contains AddonManager");
+        browser.test.assertTrue(tab.active, "Tab is active");
+        browser.test.assertTrue(tab.id != firstTab, "Tab is a new tab");
 
-        browser.test.assertEq("about:addons", optionsTab.url, "Tab contains AddonManager");
-        browser.test.assertTrue(optionsTab.active, "Tab is active");
-        browser.test.assertTrue(optionsTab.id != firstTab.id, "Tab is a new tab");
-
+        optionsTab = tab.id;
         browser.test.assertEq(0, browser.extension.getViews({type: "popup"}).length, "viewType is not popup");
         browser.test.assertEq(1, browser.extension.getViews({type: "tab"}).length, "viewType is tab");
-        browser.test.assertEq(1, browser.extension.getViews({windowId: optionsTab.windowId}).length, "windowId matches");
-
+        browser.test.assertEq(1, browser.extension.getViews({windowId: tab.windowId}).length, "windowId matches");
         let views = browser.extension.getViews();
         browser.test.assertEq(2, views.length, "Expected the options page and the background page");
         browser.test.assertTrue(views.includes(window), "One of the views is the background page");
         browser.test.assertTrue(views.some(w => w.iAmOption), "One of the views is the options page");
 
         browser.test.log("Switch tabs.");
-        await browser.tabs.update(firstTab.id, {active: true});
-
+        return browser.tabs.update(firstTab, {active: true});
+      }).then(() => {
         browser.test.log("Open options page again. Expect tab re-selected, no new load.");
 
-        await browser.runtime.openOptionsPage();
-        let [tab] = await browser.tabs.query({currentWindow: true, active: true});
-
-        browser.test.assertEq(optionsTab.id, tab.id, "Tab is the same as the previous options tab");
+        return browser.runtime.openOptionsPage();
+      }).then(() => {
+        return browser.tabs.query({currentWindow: true, active: true});
+      }).then(([tab]) => {
+        browser.test.assertEq(optionsTab, tab.id, "Tab is the same as the previous options tab");
         browser.test.assertEq("about:addons", tab.url, "Tab contains AddonManager");
 
         browser.test.log("Ping options page.");
-        let pong = await browser.runtime.sendMessage("ping");
+        return browser.runtime.sendMessage("ping");
+      }).then((pong) => {
         browser.test.assertEq("pong", pong, "Got pong.");
 
         browser.test.log("Remove options tab.");
-        await browser.tabs.remove(optionsTab.id);
-
+        return browser.tabs.remove(optionsTab);
+      }).then(() => {
         browser.test.log("Open options page again. Expect fresh load.");
-        [, tab] = await Promise.all([
+        return Promise.all([
           browser.runtime.openOptionsPage(),
           awaitOptions(),
         ]);
+      }).then(([, tab]) => {
         browser.test.assertEq("about:addons", tab.url, "Tab contains AddonManager");
         browser.test.assertTrue(tab.active, "Tab is active");
-        browser.test.assertTrue(tab.id != optionsTab.id, "Tab is a new tab");
+        browser.test.assertTrue(tab.id != optionsTab, "Tab is a new tab");
 
-        await browser.tabs.remove(tab.id);
-
+        return browser.tabs.remove(tab.id);
+      }).then(() => {
         browser.test.notifyPass("options-ui");
-      } catch (error) {
-        browser.test.fail(`Error: ${error} :: ${error.stack}`);
+      }).catch(error => {
+        browser.test.log(`Error: ${error} :: ${error.stack}`);
         browser.test.notifyFail("options-ui");
-      }
+      });
     },
   }));
 
   yield extension.awaitFinish("options-ui");
   yield extension.unload();
 
   yield BrowserTestUtils.removeTab(tab);
 });
@@ -157,17 +160,17 @@ add_tasks(function* test_tab_options(ext
     manifest: {
       applications: {gecko: {id: "tab_options@tests.mozilla.org"}},
       "options_ui": {
         "page": "options.html",
         "open_in_tab": true,
       },
     },
 
-    background: async function() {
+    background: function() {
       let _optionsPromise;
       let awaitOptions = () => {
         browser.test.assertFalse(_optionsPromise, "Should not be awaiting options already");
 
         return new Promise(resolve => {
           _optionsPromise = {resolve};
         });
       };
@@ -180,73 +183,77 @@ add_tasks(function* test_tab_options(ext
           } else {
             browser.test.fail("Saw unexpected options page load");
           }
         }
       });
 
       let optionsURL = browser.extension.getURL("options.html");
 
-      try {
-        let [firstTab] = await browser.tabs.query({currentWindow: true, active: true});
+      let firstTab, optionsTab;
+      browser.tabs.query({currentWindow: true, active: true}).then(tabs => {
+        firstTab = tabs[0].id;
 
         browser.test.log("Open options page. Expect fresh load.");
-        let [, optionsTab] = await Promise.all([
+        return Promise.all([
           browser.runtime.openOptionsPage(),
           awaitOptions(),
         ]);
-        browser.test.assertEq(optionsURL, optionsTab.url, "Tab contains options.html");
-        browser.test.assertTrue(optionsTab.active, "Tab is active");
-        browser.test.assertTrue(optionsTab.id != firstTab.id, "Tab is a new tab");
+      }).then(([, tab]) => {
+        browser.test.assertEq(optionsURL, tab.url, "Tab contains options.html");
+        browser.test.assertTrue(tab.active, "Tab is active");
+        browser.test.assertTrue(tab.id != firstTab, "Tab is a new tab");
 
+        optionsTab = tab.id;
         browser.test.assertEq(0, browser.extension.getViews({type: "popup"}).length, "viewType is not popup");
         browser.test.assertEq(1, browser.extension.getViews({type: "tab"}).length, "viewType is tab");
-        browser.test.assertEq(1, browser.extension.getViews({windowId: optionsTab.windowId}).length, "windowId matches");
-
+        browser.test.assertEq(1, browser.extension.getViews({windowId: tab.windowId}).length, "windowId matches");
         let views = browser.extension.getViews();
         browser.test.assertEq(2, views.length, "Expected the options page and the background page");
         browser.test.assertTrue(views.includes(window), "One of the views is the background page");
         browser.test.assertTrue(views.some(w => w.iAmOption), "One of the views is the options page");
 
         browser.test.log("Switch tabs.");
-        await browser.tabs.update(firstTab.id, {active: true});
-
+        return browser.tabs.update(firstTab, {active: true});
+      }).then(() => {
         browser.test.log("Open options page again. Expect tab re-selected, no new load.");
 
-        await browser.runtime.openOptionsPage();
-        let [tab] = await browser.tabs.query({currentWindow: true, active: true});
-
-        browser.test.assertEq(optionsTab.id, tab.id, "Tab is the same as the previous options tab");
+        return browser.runtime.openOptionsPage();
+      }).then(() => {
+        return browser.tabs.query({currentWindow: true, active: true});
+      }).then(([tab]) => {
+        browser.test.assertEq(optionsTab, tab.id, "Tab is the same as the previous options tab");
         browser.test.assertEq(optionsURL, tab.url, "Tab contains options.html");
 
         // Unfortunately, we can't currently do this, since onMessage doesn't
         // currently support responses when there are multiple listeners.
         //
         // browser.test.log("Ping options page.");
         // return new Promise(resolve => browser.runtime.sendMessage("ping", resolve));
 
         browser.test.log("Remove options tab.");
-        await browser.tabs.remove(optionsTab.id);
-
+        return browser.tabs.remove(optionsTab);
+      }).then(() => {
         browser.test.log("Open options page again. Expect fresh load.");
-        [, tab] = await Promise.all([
+        return Promise.all([
           browser.runtime.openOptionsPage(),
           awaitOptions(),
         ]);
+      }).then(([, tab]) => {
         browser.test.assertEq(optionsURL, tab.url, "Tab contains options.html");
         browser.test.assertTrue(tab.active, "Tab is active");
-        browser.test.assertTrue(tab.id != optionsTab.id, "Tab is a new tab");
+        browser.test.assertTrue(tab.id != optionsTab, "Tab is a new tab");
 
-        await browser.tabs.remove(tab.id);
-
+        return browser.tabs.remove(tab.id);
+      }).then(() => {
         browser.test.notifyPass("options-ui-tab");
-      } catch (error) {
-        browser.test.fail(`Error: ${error} :: ${error.stack}`);
+      }).catch(error => {
+        browser.test.log(`Error: ${error} :: ${error.stack}`);
         browser.test.notifyFail("options-ui-tab");
-      }
+      });
     },
   }));
 
   yield extension.awaitFinish("options-ui-tab");
   yield extension.unload();
 
   yield BrowserTestUtils.removeTab(tab);
 });
@@ -271,17 +278,17 @@ add_tasks(function* test_options_no_mani
           let expected = "No `options_ui` declared";
           browser.test.assertTrue(
             error.message.includes(expected),
             `Got expected error (got: '${error.message}', expected: '${expected}'`);
         }
       ).then(() => {
         browser.test.notifyPass("options-no-manifest");
       }).catch(error => {
-        browser.test.fail(`Error: ${error} :: ${error.stack}`);
+        browser.test.log(`Error: ${error} :: ${error.stack}`);
         browser.test.notifyFail("options-no-manifest");
       });
     },
   }));
 
   yield extension.awaitFinish("options-no-manifest");
   yield extension.unload();
 });

--- a/browser/components/extensions/test/browser/browser_ext_runtime_openOptionsPage_uninstall.js
+++ b/browser/components/extensions/test/browser/browser_ext_runtime_openOptionsPage_uninstall.js
@@ -43,17 +43,17 @@ add_task(function* test_inline_options_u
   let extension = yield loadExtension({
     manifest: {
       applications: {gecko: {id: "inline_options_uninstall@tests.mozilla.org"}},
       "options_ui": {
         "page": "options.html",
       },
     },
 
-    background: async function() {
+    background: function() {
       let _optionsPromise;
       let awaitOptions = () => {
         browser.test.assertFalse(_optionsPromise, "Should not be awaiting options already");
 
         return new Promise(resolve => {
           _optionsPromise = {resolve};
         });
       };
@@ -64,33 +64,34 @@ add_task(function* test_inline_options_u
             _optionsPromise.resolve(sender.tab);
             _optionsPromise = null;
           } else {
             browser.test.fail("Saw unexpected options page load");
           }
         }
       });
 
-      try {
-        let [firstTab] = await browser.tabs.query({currentWindow: true, active: true});
+      let firstTab;
+      browser.tabs.query({currentWindow: true, active: true}).then(tabs => {
+        firstTab = tabs[0].id;
 
         browser.test.log("Open options page. Expect fresh load.");
-        let [, tab] = await Promise.all([
+        return Promise.all([
           browser.runtime.openOptionsPage(),
           awaitOptions(),
         ]);
-
+      }).then(([, tab]) => {
         browser.test.assertEq("about:addons", tab.url, "Tab contains AddonManager");
         browser.test.assertTrue(tab.active, "Tab is active");
-        browser.test.assertTrue(tab.id != firstTab.id, "Tab is a new tab");
+        browser.test.assertTrue(tab.id != firstTab, "Tab is a new tab");
 
         browser.test.sendMessage("options-ui-open");
-      } catch (error) {
+      }).catch(error => {
         browser.test.fail(`Error: ${error} :: ${error.stack}`);
-      }
+      });
     },
   });
 
   yield extension.awaitMessage("options-ui-open");
   yield extension.unload();
 
   is(gBrowser.selectedBrowser.currentURI.spec, "about:addons",
      "Add-on manager tab should still be open");

--- a/browser/components/extensions/test/browser/browser_ext_runtime_setUninstallURL.js
+++ b/browser/components/extensions/test/browser/browser_ext_runtime_setUninstallURL.js
@@ -25,17 +25,17 @@ function* makeAndInstallXPI(id, backgrou
   let loadTab = yield loadPromise;
   yield BrowserTestUtils.removeTab(loadTab);
 
   return addon;
 }
 
 
 add_task(function* test_setuninstallurl_badargs() {
-  async function backgroundScript() {
+  function backgroundScript() {
     let promises = [
       browser.runtime.setUninstallURL("this is not a url")
         .then(() => {
           browser.test.notifyFail("setUninstallURL should have failed with bad url");
         })
         .catch(error => {
           browser.test.assertTrue(/Invalid URL/.test(error.message), "error message indicates malformed url");
         }),
@@ -44,52 +44,52 @@ add_task(function* test_setuninstallurl_
         .then(() => {
           browser.test.notifyFail("setUninstallURL should have failed with non-http[s] url");
         })
         .catch(error => {
           browser.test.assertTrue(/must have the scheme http or https/.test(error.message), "error message indicates bad scheme");
         }),
     ];
 
-    await Promise.all(promises);
-    browser.test.notifyPass("setUninstallURL bad params");
+    Promise.all(promises)
+      .then(() => browser.test.notifyPass("setUninstallURL bad params"));
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     background: "(" + backgroundScript.toString() + ")()",
   });
   yield extension.startup();
   yield extension.awaitFinish();
   yield extension.unload();
 });
 
 // Test the documented behavior of setUninstallURL() that passing an
 // empty string is equivalent to not setting an uninstall URL
 // (i.e., no new tab is opened upon uninstall)
 add_task(function* test_setuninstall_empty_url() {
-  async function backgroundScript() {
-    await browser.runtime.setUninstallURL("");
-    browser.tabs.create({url: "http://example.com/addon_loaded"});
+  function backgroundScript() {
+    browser.runtime.setUninstallURL("")
+      .then(() => browser.tabs.create({url: "http://example.com/addon_loaded"}));
   }
 
   let addon = yield makeAndInstallXPI("test_uinstallurl2@tests.mozilla.org",
                                       backgroundScript,
                                       "http://example.com/addon_loaded");
 
   addon.uninstall(true);
   info("uninstalled");
 
   // no need to explicitly check for the absence of a new tab,
   // BrowserTestUtils will eventually complain if one is opened.
 });
 
 add_task(function* test_setuninstallurl() {
-  async function backgroundScript() {
-    await browser.runtime.setUninstallURL("http://example.com/addon_uninstalled");
-    browser.tabs.create({url: "http://example.com/addon_loaded"});
+  function backgroundScript() {
+    browser.runtime.setUninstallURL("http://example.com/addon_uninstalled")
+      .then(() => browser.tabs.create({url: "http://example.com/addon_loaded"}));
   }
 
   let addon = yield makeAndInstallXPI("test_uinstallurl@tests.mozilla.org",
                                       backgroundScript,
                                       "http://example.com/addon_loaded");
 
   // look for a new tab with the uninstall url.
   let uninstallPromise = BrowserTestUtils.waitForNewTab(gBrowser, "http://example.com/addon_uninstalled");

--- a/browser/components/extensions/test/browser/browser_ext_tabs_audio.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_audio.js
@@ -3,17 +3,27 @@
 "use strict";
 
 add_task(function* () {
   let tab1 = yield BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank?1");
   let tab2 = yield BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank?2");
 
   gBrowser.selectedTab = tab1;
 
-  async function background() {
+  function background() {
+    // Wrap API methods in promise-based variants.
+    let promiseTabs = {};
+    Object.keys(browser.tabs).forEach(method => {
+      promiseTabs[method] = (...args) => {
+        return new Promise(resolve => {
+          browser.tabs[method](...args, resolve);
+        });
+      };
+    });
+
     function promiseUpdated(tabId, attr) {
       return new Promise(resolve => {
         let onUpdated = (tabId_, changeInfo, tab) => {
           if (tabId == tabId_ && attr in changeInfo) {
             browser.tabs.onUpdated.removeListener(onUpdated);
 
             resolve({changeInfo, tab});
           }
@@ -32,129 +42,134 @@ add_task(function* () {
     function changeTab(tabId, attr, on) {
       return new Promise((resolve, reject) => {
         deferred[tabId] = {resolve, reject};
         browser.test.sendMessage("change-tab", tabId, attr, on);
       });
     }
 
 
-    try {
-      let tabs = await browser.tabs.query({lastFocusedWindow: true});
+    let windowId;
+    let tabIds;
+    promiseTabs.query({lastFocusedWindow: true}).then(tabs => {
       browser.test.assertEq(tabs.length, 3, "We have three tabs");
 
       for (let tab of tabs) {
         // Note: We want to check that these are actual boolean values, not
         // just that they evaluate as false.
         browser.test.assertEq(false, tab.mutedInfo.muted, "Tab is not muted");
         browser.test.assertEq(undefined, tab.mutedInfo.reason, "Tab has no muted info reason");
         browser.test.assertEq(false, tab.audible, "Tab is not audible");
       }
 
-      let windowId = tabs[0].windowId;
-      let tabIds = [tabs[1].id, tabs[2].id];
+      windowId = tabs[0].windowId;
+      tabIds = [tabs[1].id, tabs[2].id];
 
       browser.test.log("Test initial queries for muted and audible return no tabs");
-      let silent = await browser.tabs.query({windowId, audible: false});
-      let audible = await browser.tabs.query({windowId, audible: true});
-      let muted = await browser.tabs.query({windowId, muted: true});
-      let nonMuted = await browser.tabs.query({windowId, muted: false});
-
+      return Promise.all([
+        promiseTabs.query({windowId, audible: false}),
+        promiseTabs.query({windowId, audible: true}),
+        promiseTabs.query({windowId, muted: true}),
+        promiseTabs.query({windowId, muted: false}),
+      ]);
+    }).then(([silent, audible, muted, nonMuted]) => {
       browser.test.assertEq(3, silent.length, "Three silent tabs");
       browser.test.assertEq(0, audible.length, "No audible tabs");
 
       browser.test.assertEq(0, muted.length, "No muted tabs");
       browser.test.assertEq(3, nonMuted.length, "Three non-muted tabs");
 
       browser.test.log("Toggle muted and audible externally on one tab each, and check results");
-      [muted, audible] = await Promise.all([
+      return Promise.all([
         promiseUpdated(tabIds[0], "mutedInfo"),
         promiseUpdated(tabIds[1], "audible"),
         changeTab(tabIds[0], "muted", true),
         changeTab(tabIds[1], "audible", true),
       ]);
-
+    }).then(([muted, audible]) => {
       for (let obj of [muted.changeInfo, muted.tab]) {
         browser.test.assertEq(true, obj.mutedInfo.muted, "Tab is muted");
         browser.test.assertEq("user", obj.mutedInfo.reason, "Tab was muted by the user");
       }
 
       browser.test.assertEq(true, audible.changeInfo.audible, "Tab audible state changed");
       browser.test.assertEq(true, audible.tab.audible, "Tab is audible");
 
       browser.test.log("Re-check queries. Expect one audible and one muted tab");
-      silent = await browser.tabs.query({windowId, audible: false});
-      audible = await browser.tabs.query({windowId, audible: true});
-      muted = await browser.tabs.query({windowId, muted: true});
-      nonMuted = await browser.tabs.query({windowId, muted: false});
-
+      return Promise.all([
+        promiseTabs.query({windowId, audible: false}),
+        promiseTabs.query({windowId, audible: true}),
+        promiseTabs.query({windowId, muted: true}),
+        promiseTabs.query({windowId, muted: false}),
+      ]);
+    }).then(([silent, audible, muted, nonMuted]) => {
       browser.test.assertEq(2, silent.length, "Two silent tabs");
       browser.test.assertEq(1, audible.length, "One audible tab");
 
       browser.test.assertEq(1, muted.length, "One muted tab");
       browser.test.assertEq(2, nonMuted.length, "Two non-muted tabs");
 
       browser.test.assertEq(true, muted[0].mutedInfo.muted, "Tab is muted");
       browser.test.assertEq("user", muted[0].mutedInfo.reason, "Tab was muted by the user");
 
       browser.test.assertEq(true, audible[0].audible, "Tab is audible");
 
       browser.test.log("Toggle muted internally on two tabs, and check results");
-      [nonMuted, muted] = await Promise.all([
+      return Promise.all([
         promiseUpdated(tabIds[0], "mutedInfo"),
         promiseUpdated(tabIds[1], "mutedInfo"),
-        browser.tabs.update(tabIds[0], {muted: false}),
-        browser.tabs.update(tabIds[1], {muted: true}),
+        promiseTabs.update(tabIds[0], {muted: false}),
+        promiseTabs.update(tabIds[1], {muted: true}),
       ]);
-
-      for (let obj of [nonMuted.changeInfo, nonMuted.tab]) {
+    }).then(([unmuted, muted]) => {
+      for (let obj of [unmuted.changeInfo, unmuted.tab]) {
         browser.test.assertEq(false, obj.mutedInfo.muted, "Tab is not muted");
       }
       for (let obj of [muted.changeInfo, muted.tab]) {
         browser.test.assertEq(true, obj.mutedInfo.muted, "Tab is muted");
       }
 
-      for (let obj of [nonMuted.changeInfo, nonMuted.tab, muted.changeInfo, muted.tab]) {
+      for (let obj of [unmuted.changeInfo, unmuted.tab, muted.changeInfo, muted.tab]) {
         browser.test.assertEq("extension", obj.mutedInfo.reason, "Mute state changed by extension");
 
         // FIXME: browser.runtime.id is currently broken.
         browser.test.assertEq(browser.i18n.getMessage("@@extension_id"),
                               obj.mutedInfo.extensionId,
                               "Mute state changed by extension");
       }
 
       browser.test.log("Test that mutedInfo is preserved by sessionstore");
-      let tab = await changeTab(tabIds[1], "duplicate").then(browser.tabs.get);
-
+      return changeTab(tabIds[1], "duplicate").then(promiseTabs.get);
+    }).then(tab => {
       browser.test.assertEq(true, tab.mutedInfo.muted, "Tab is muted");
 
       browser.test.assertEq("extension", tab.mutedInfo.reason, "Mute state changed by extension");
 
       // FIXME: browser.runtime.id is currently broken.
       browser.test.assertEq(browser.i18n.getMessage("@@extension_id"),
                             tab.mutedInfo.extensionId,
                             "Mute state changed by extension");
 
       browser.test.log("Unmute externally, and check results");
-      [nonMuted] = await Promise.all([
+      return Promise.all([
         promiseUpdated(tabIds[1], "mutedInfo"),
         changeTab(tabIds[1], "muted", false),
-        browser.tabs.remove(tab.id),
+        promiseTabs.remove(tab.id),
       ]);
-
-      for (let obj of [nonMuted.changeInfo, nonMuted.tab]) {
+    }).then(([unmuted]) => {
+      for (let obj of [unmuted.changeInfo, unmuted.tab]) {
         browser.test.assertEq(false, obj.mutedInfo.muted, "Tab is not muted");
         browser.test.assertEq("user", obj.mutedInfo.reason, "Mute state changed by user");
       }
 
       browser.test.notifyPass("tab-audio");
-    } catch (e) {
+    }).catch(e => {
       browser.test.fail(`${e} :: ${e.stack}`);
       browser.test.notifyFail("tab-audio");
-    }
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["tabs"],
     },
 
     background,

--- a/browser/components/extensions/test/browser/browser_ext_tabs_captureVisibleTab.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_captureVisibleTab.js
@@ -21,95 +21,103 @@ function* runTest(options) {
     </html>
   `;
 
   let url = `data:text/html,${encodeURIComponent(html)}`;
   let tab = yield BrowserTestUtils.openNewForegroundTab(gBrowser, url, true);
 
   tab.linkedBrowser.fullZoom = options.fullZoom;
 
-  async function background(options) {
+  function background(options) {
+    // Wrap API methods in promise-based variants.
+    let promiseTabs = {};
+    Object.keys(browser.tabs).forEach(method => {
+      promiseTabs[method] = (...args) => {
+        return new Promise(resolve => {
+          browser.tabs[method](...args, resolve);
+        });
+      };
+    });
+
     browser.test.log(`Test color ${options.color} at fullZoom=${options.fullZoom}`);
 
-    try {
-      let [tab] = await browser.tabs.query({currentWindow: true, active: true});
+    promiseTabs.query({currentWindow: true, active: true}).then(([tab]) => {
+      return Promise.all([
+        promiseTabs.captureVisibleTab(tab.windowId, {format: "jpeg", quality: 95}),
+        promiseTabs.captureVisibleTab(tab.windowId, {format: "png", quality: 95}),
+        promiseTabs.captureVisibleTab(tab.windowId, {quality: 95}),
+        promiseTabs.captureVisibleTab(tab.windowId),
+      ]).then(([jpeg, png, ...pngs]) => {
+        browser.test.assertTrue(pngs.every(url => url == png), "All PNGs are identical");
 
-      let [jpeg, png, ...pngs] = await Promise.all([
-        browser.tabs.captureVisibleTab(tab.windowId, {format: "jpeg", quality: 95}),
-        browser.tabs.captureVisibleTab(tab.windowId, {format: "png", quality: 95}),
-        browser.tabs.captureVisibleTab(tab.windowId, {quality: 95}),
-        browser.tabs.captureVisibleTab(tab.windowId),
-      ]);
-
-      browser.test.assertTrue(pngs.every(url => url == png), "All PNGs are identical");
-
-      browser.test.assertTrue(jpeg.startsWith("data:image/jpeg;base64,"), "jpeg is JPEG");
-      browser.test.assertTrue(png.startsWith("data:image/png;base64,"), "png is PNG");
+        browser.test.assertTrue(jpeg.startsWith("data:image/jpeg;base64,"), "jpeg is JPEG");
+        browser.test.assertTrue(png.startsWith("data:image/png;base64,"), "png is PNG");
 
-      let promises = [jpeg, png].map(url => new Promise(resolve => {
-        let img = new Image();
-        img.src = url;
-        img.onload = () => resolve(img);
-      }));
+        let promises = [jpeg, png].map(url => new Promise(resolve => {
+          let img = new Image();
+          img.src = url;
+          img.onload = () => resolve(img);
+        }));
+        return Promise.all(promises);
+      }).then(([jpeg, png]) => {
+        let tabDims = `${tab.width}\u00d7${tab.height}`;
 
-      [jpeg, png] = await Promise.all(promises);
-      let tabDims = `${tab.width}\u00d7${tab.height}`;
+        let images = {jpeg, png};
+        for (let format of Object.keys(images)) {
+          let img = images[format];
 
-      let images = {jpeg, png};
-      for (let format of Object.keys(images)) {
-        let img = images[format];
+          let dims = `${img.width}\u00d7${img.height}`;
+          browser.test.assertEq(tabDims, dims, `${format} dimensions are correct`);
 
-        let dims = `${img.width}\u00d7${img.height}`;
-        browser.test.assertEq(tabDims, dims, `${format} dimensions are correct`);
+          let canvas = document.createElement("canvas");
+          canvas.width = img.width;
+          canvas.height = img.height;
+          canvas.mozOpaque = true;
 
-        let canvas = document.createElement("canvas");
-        canvas.width = img.width;
-        canvas.height = img.height;
-        canvas.mozOpaque = true;
+          let ctx = canvas.getContext("2d");
+          ctx.drawImage(img, 0, 0);
 
-        let ctx = canvas.getContext("2d");
-        ctx.drawImage(img, 0, 0);
+          // Check the colors of the first and last pixels of the image, to make
+          // sure we capture the entire frame, and scale it correctly.
+          let coords = [
+            {x: 0, y: 0,
+             color: options.color},
+            {x: img.width - 1,
+             y: img.height - 1,
+             color: options.color},
+            {x: img.width / 2 | 0,
+             y: img.height / 2 | 0,
+             color: options.neutral},
+          ];
 
-        // Check the colors of the first and last pixels of the image, to make
-        // sure we capture the entire frame, and scale it correctly.
-        let coords = [
-          {x: 0, y: 0,
-           color: options.color},
-          {x: img.width - 1,
-           y: img.height - 1,
-           color: options.color},
-          {x: img.width / 2 | 0,
-           y: img.height / 2 | 0,
-           color: options.neutral},
-        ];
+          for (let {x, y, color} of coords) {
+            let imageData = ctx.getImageData(x, y, 1, 1).data;
 
-        for (let {x, y, color} of coords) {
-          let imageData = ctx.getImageData(x, y, 1, 1).data;
+            if (format == "png") {
+              browser.test.assertEq(`rgba(${color},255)`, `rgba(${[...imageData]})`, `${format} image color is correct at (${x}, ${y})`);
+            } else {
+              // Allow for some deviation in JPEG version due to lossy compression.
+              const SLOP = 3;
 
-          if (format == "png") {
-            browser.test.assertEq(`rgba(${color},255)`, `rgba(${[...imageData]})`, `${format} image color is correct at (${x}, ${y})`);
-          } else {
-            // Allow for some deviation in JPEG version due to lossy compression.
-            const SLOP = 3;
+              browser.test.log(`Testing ${format} image color at (${x}, ${y}), have rgba(${[...imageData]}), expecting approx. rgba(${color},255)`);
 
-            browser.test.log(`Testing ${format} image color at (${x}, ${y}), have rgba(${[...imageData]}), expecting approx. rgba(${color},255)`);
-
-            browser.test.assertTrue(Math.abs(color[0] - imageData[0]) <= SLOP, `${format} image color.red is correct at (${x}, ${y})`);
-            browser.test.assertTrue(Math.abs(color[1] - imageData[1]) <= SLOP, `${format} image color.green is correct at (${x}, ${y})`);
-            browser.test.assertTrue(Math.abs(color[2] - imageData[2]) <= SLOP, `${format} image color.blue is correct at (${x}, ${y})`);
-            browser.test.assertEq(255, imageData[3], `${format} image color.alpha is correct at (${x}, ${y})`);
+              browser.test.assertTrue(Math.abs(color[0] - imageData[0]) <= SLOP, `${format} image color.red is correct at (${x}, ${y})`);
+              browser.test.assertTrue(Math.abs(color[1] - imageData[1]) <= SLOP, `${format} image color.green is correct at (${x}, ${y})`);
+              browser.test.assertTrue(Math.abs(color[2] - imageData[2]) <= SLOP, `${format} image color.blue is correct at (${x}, ${y})`);
+              browser.test.assertEq(255, imageData[3], `${format} image color.alpha is correct at (${x}, ${y})`);
+            }
           }
         }
-      }
 
-      browser.test.notifyPass("captureVisibleTab");
-    } catch (e) {
+        browser.test.notifyPass("captureVisibleTab");
+      });
+    }).catch(e => {
       browser.test.fail(`Error: ${e} :: ${e.stack}`);
       browser.test.notifyFail("captureVisibleTab");
-    }
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["<all_urls>"],
     },
 
     background: `(${background})(${JSON.stringify(options)})`,

--- a/browser/components/extensions/test/browser/browser_ext_tabs_cookieStoreId.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_cookieStoreId.js
@@ -37,89 +37,107 @@ add_task(function* () {
 
     background: function() {
       function testTab(data, tab) {
         browser.test.assertTrue(data.success, "we want a success");
         browser.test.assertTrue(!!tab, "we have a tab");
         browser.test.assertEq(data.expectedCookieStoreId, tab.cookieStoreId, "tab should have the correct cookieStoreId");
       }
 
-      async function runTest(data) {
-        try {
-          // Tab Creation
-          let tab = await browser.tabs.create({
-            windowId: data.privateTab ? this.privateWindowId : this.defaultWindowId,
-            cookieStoreId: data.cookieStoreId,
-          }).then((tab) => {
-            // Tests for tab creation
-            testTab(data, tab);
-            return tab;
-          }, (error) => {
-            browser.test.assertTrue(!!data.failure, "we want a failure");
-            if (data.failure == "illegal") {
-              browser.test.assertTrue(/Illegal cookieStoreId/.test(error.message),
-                                      "runtime.lastError should report the expected error message");
-            } else if (data.failure == "defaultToPrivate") {
-              browser.test.assertTrue("Illegal to set private cookieStorageId in a non private window",
-                                      error.message,
-                                      "runtime.lastError should report the expected error message");
-            } else if (data.failure == "privateToDefault") {
-              browser.test.assertTrue("Illegal to set non private cookieStorageId in a private window",
-                                      error.message,
-                                      "runtime.lastError should report the expected error message");
-            } else if (data.failure == "exist") {
-              browser.test.assertTrue(/No cookie store exists/.test(error.message),
-                                      "runtime.lastError should report the expected error message");
-            } else {
-              browser.test.fail("The test is broken");
-            }
+      function runTest(data) {
+        // Tab Creation
+        browser.tabs.create({windowId: data.privateTab ? this.privateWindowId : this.defaultWindowId,
+                             cookieStoreId: data.cookieStoreId})
 
-            return null;
-          });
-
-          if (tab) {
-            {
-              // Tests for tab querying
-              let [tab] = await browser.tabs.query({
-                windowId: data.privateTab ? this.privateWindowId : this.defaultWindowId,
-                cookieStoreId: data.cookieStoreId,
-              });
-
-              browser.test.assertTrue(tab != undefined, "Tab found!");
-              testTab(data, tab);
-            }
-
-            let stores = await browser.cookies.getAllCookieStores();
-
-            let store = stores.find(store => store.id === tab.cookieStoreId);
-            browser.test.assertTrue(!!store, "We have a store for this tab.");
-
-            await browser.tabs.remove(tab.id);
+        // Tests for tab creation
+        .then((tab) => {
+          testTab(data, tab);
+          return tab;
+        }, (error) => {
+          browser.test.assertTrue(!!data.failure, "we want a failure");
+          if (data.failure == "illegal") {
+            browser.test.assertTrue(/Illegal cookieStoreId/.test(error.message),
+                                    "runtime.lastError should report the expected error message");
+          } else if (data.failure == "defaultToPrivate") {
+            browser.test.assertTrue("Illegal to set private cookieStorageId in a non private window",
+                                    error.message,
+                                    "runtime.lastError should report the expected error message");
+          } else if (data.failure == "privateToDefault") {
+            browser.test.assertTrue("Illegal to set non private cookieStorageId in a private window",
+                                    error.message,
+                                    "runtime.lastError should report the expected error message");
+          } else if (data.failure == "exist") {
+            browser.test.assertTrue(/No cookie store exists/.test(error.message),
+                                    "runtime.lastError should report the expected error message");
+          } else {
+            browser.test.fail("The test is broken");
           }
 
+          return null;
+        })
+
+        // Tests for tab querying
+        .then((tab) => {
+          if (tab) {
+            return browser.tabs.query({windowId: data.privateTab ? this.privateWindowId : this.defaultWindowId,
+                                       cookieStoreId: data.cookieStoreId})
+                   .then((tabs) => {
+                     browser.test.assertTrue(tabs.length >= 1, "Tab found!");
+                     testTab(data, tabs[0]);
+                     return tab;
+                   });
+          }
+        })
+
+        .then((tab) => {
+          if (tab) {
+            return browser.cookies.getAllCookieStores()
+                   .then(stores => {
+                     let store = stores.find(store => store.id === tab.cookieStoreId);
+                     browser.test.assertTrue(!!store, "We have a store for this tab.");
+                     return tab;
+                   });
+          }
+        })
+
+        .then((tab) => {
+          if (tab) {
+            return browser.tabs.remove(tab.id);
+          }
+        })
+
+        .then(() => {
           browser.test.sendMessage("test-done");
-        } catch (e) {
-          browser.test.fail("An exception has been thrown");
-        }
+        }, () => {
+          browser.test.fail("An exception has ben thrown");
+        });
       }
 
-      async function initialize() {
-        let win = await browser.windows.create({incognito: true});
-        this.privateWindowId = win.id;
-
-        win = await browser.windows.create({incognito: false});
-        this.defaultWindowId = win.id;
-
-        browser.test.sendMessage("ready");
+      function initialize() {
+        browser.windows.create({incognito: true})
+        .then((win) => {
+          this.privateWindowId = win.id;
+          return browser.windows.create({incognito: false});
+        })
+        .then((win) => {
+          this.defaultWindowId = win.id;
+        })
+        .then(() => {
+          browser.test.sendMessage("ready");
+        });
       }
 
-      async function shutdown() {
-        await browser.windows.remove(this.privateWindowId);
-        await browser.windows.remove(this.defaultWindowId);
-        browser.test.sendMessage("gone");
+      function shutdown() {
+        browser.windows.remove(this.privateWindowId)
+        .then(() => {
+          browser.windows.remove(this.defaultWindowId);
+        })
+        .then(() => {
+          browser.test.sendMessage("gone");
+        });
       }
 
       // Waiting for messages
       browser.test.onMessage.addListener((msg, data) => {
         if (msg == "be-ready") {
           initialize();
         } else if (msg == "test") {
           runTest(data);

--- a/browser/components/extensions/test/browser/browser_ext_tabs_create.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_create.js
@@ -85,17 +85,17 @@ add_task(function* () {
               result: {index: 1, active: false},
             },
             {
               create: {windowId: activeWindow},
               result: {windowId: activeWindow},
             },
           ];
 
-          async function nextTest() {
+          function nextTest() {
             if (!tests.length) {
               browser.test.notifyPass("tabs.create");
               return;
             }
 
             let test = tests.shift();
             let expected = Object.assign({}, DEFAULTS, test.result);
 
@@ -114,39 +114,43 @@ add_task(function* () {
             let createdPromise = new Promise(resolve => {
               let onCreated = tab => {
                 browser.test.assertTrue("id" in tab, `Expected tabs.onCreated callback to receive tab object`);
                 resolve();
               };
               browser.tabs.onCreated.addListener(onCreated);
             });
 
-            let [tab] = await Promise.all([
+            let tabId;
+            Promise.all([
               browser.tabs.create(test.create),
               createdPromise,
-            ]);
-            let tabId = tab.id;
+            ]).then(([tab]) => {
+              tabId = tab.id;
 
-            for (let key of Object.keys(expected)) {
-              if (key === "url") {
-                // FIXME: This doesn't get updated until later in the load cycle.
-                continue;
+              for (let key of Object.keys(expected)) {
+                if (key === "url") {
+                  // FIXME: This doesn't get updated until later in the load cycle.
+                  continue;
+                }
+
+                browser.test.assertEq(expected[key], tab[key], `Expected value for tab.${key}`);
               }
 
-              browser.test.assertEq(expected[key], tab[key], `Expected value for tab.${key}`);
-            }
+              return updatedPromise;
+            }).then(updated => {
+              browser.test.assertEq(tabId, updated.tabId, `Expected value for tab.id`);
+              browser.test.assertEq(expected.url, updated.url, `Expected value for tab.url`);
 
-            let updated = await updatedPromise;
-            browser.test.assertEq(tabId, updated.tabId, `Expected value for tab.id`);
-            browser.test.assertEq(expected.url, updated.url, `Expected value for tab.url`);
-
-            await browser.tabs.remove(tabId);
-            await browser.tabs.update(activeTab, {active: true});
-
-            nextTest();
+              return browser.tabs.remove(tabId);
+            }).then(() => {
+              return browser.tabs.update(activeTab, {active: true});
+            }).then(() => {
+              nextTest();
+            });
           }
 
           nextTest();
         }
 
         browser.tabs.query({active: true, currentWindow: true}, tabs => {
           activeTab = tabs[0].id;
           activeWindow = tabs[0].windowId;

--- a/browser/components/extensions/test/browser/browser_ext_tabs_detectLanguage.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_detectLanguage.js
@@ -3,44 +3,48 @@
 "use strict";
 
 add_task(function* testDetectLanguage() {
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["tabs"],
     },
 
-    background: async function() {
+    background() {
       const BASE_PATH = "browser/browser/components/extensions/test/browser";
 
       function loadTab(url) {
         return browser.tabs.create({url});
       }
 
-      try {
-        let tab = await loadTab(`http://example.co.jp/${BASE_PATH}/file_language_ja.html`);
-        let lang = await browser.tabs.detectLanguage(tab.id);
-        browser.test.assertEq("ja", lang, "Japanese document should be detected as Japanese");
-        await browser.tabs.remove(tab.id);
-
-        tab = await loadTab(`http://example.co.jp/${BASE_PATH}/file_language_fr_en.html`);
-        lang = await browser.tabs.detectLanguage(tab.id);
-        browser.test.assertEq("fr", lang, "French/English document should be detected as primarily French");
-        await browser.tabs.remove(tab.id);
-
-        tab = await loadTab(`http://example.co.jp/${BASE_PATH}/file_language_tlh.html`);
-        lang = await browser.tabs.detectLanguage(tab.id);
-        browser.test.assertEq("und", lang, "Klingon document should not be detected, should return 'und'");
-        await browser.tabs.remove(tab.id);
-
+      loadTab(`http://example.co.jp/${BASE_PATH}/file_language_ja.html`).then(tab => {
+        return browser.tabs.detectLanguage(tab.id).then(lang => {
+          browser.test.assertEq("ja", lang, "Japanese document should be detected as Japanese");
+          return browser.tabs.remove(tab.id);
+        });
+      }).then(() => {
+        return loadTab(`http://example.co.jp/${BASE_PATH}/file_language_fr_en.html`);
+      }).then(tab => {
+        return browser.tabs.detectLanguage(tab.id).then(lang => {
+          browser.test.assertEq("fr", lang, "French/English document should be detected as primarily French");
+          return browser.tabs.remove(tab.id);
+        });
+      }).then(() => {
+        return loadTab(`http://example.co.jp/${BASE_PATH}/file_language_tlh.html`);
+      }).then(tab => {
+        return browser.tabs.detectLanguage(tab.id).then(lang => {
+          browser.test.assertEq("und", lang, "Klingon document should not be detected, should return 'und'");
+          return browser.tabs.remove(tab.id);
+        });
+      }).then(() => {
         browser.test.notifyPass("detectLanguage");
-      } catch (e) {
+      }).catch(e => {
         browser.test.fail(`Error: ${e} :: ${e.stack}`);
         browser.test.notifyFail("detectLanguage");
-      }
+      });
     },
   });
 
   yield extension.startup();
 
   yield extension.awaitFinish("detectLanguage");
 
   yield extension.unload();

--- a/browser/components/extensions/test/browser/browser_ext_tabs_duplicate.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_duplicate.js
@@ -36,17 +36,17 @@ add_task(function* testDuplicateTab() {
   yield extension.unload();
 
   while (gBrowser.tabs[0].linkedBrowser.currentURI.spec === "http://example.net/") {
     yield BrowserTestUtils.removeTab(gBrowser.tabs[0]);
   }
 });
 
 add_task(function* testDuplicateTabLazily() {
-  async function background() {
+  function background() {
     let tabLoadComplete = new Promise(resolve => {
       browser.test.onMessage.addListener((message, tabId, result) => {
         if (message == "duplicate-tab-done") {
           resolve(tabId);
         }
       });
     });
 
@@ -56,38 +56,42 @@ add_task(function* testDuplicateTabLazil
           if (tabId == tabId_ && changed.status == "complete") {
             browser.tabs.onUpdated.removeListener(listener);
             resolve();
           }
         });
       });
     }
 
-    try {
-      let url = "http://example.com/browser/browser/components/extensions/test/browser/file_dummy.html";
-      let tab = await browser.tabs.create({url});
-      let startTabId = tab.id;
+    let startTabId;
+    let url = "http://example.com/browser/browser/components/extensions/test/browser/file_dummy.html";
+    browser.tabs.create({url}, tab => {
+      startTabId = tab.id;
 
-      await awaitLoad(startTabId);
-      browser.test.sendMessage("duplicate-tab", startTabId);
+      awaitLoad(startTabId).then(() => {
+        browser.test.sendMessage("duplicate-tab", startTabId);
 
-      let unloadedTabId = await tabLoadComplete;
-      let loadedtab = await browser.tabs.get(startTabId);
-      browser.test.assertEq("Dummy test page", loadedtab.title, "Title should be returned for loaded pages");
-      browser.test.assertEq("complete", loadedtab.status, "Tab status should be complete for loaded pages");
+        tabLoadComplete.then(unloadedTabId => {
+          browser.tabs.get(startTabId, loadedtab => {
+            browser.test.assertEq("Dummy test page", loadedtab.title, "Title should be returned for loaded pages");
+            browser.test.assertEq("complete", loadedtab.status, "Tab status should be complete for loaded pages");
+          });
 
-      let unloadedtab = await browser.tabs.get(unloadedTabId);
-      browser.test.assertEq("Dummy test page", unloadedtab.title, "Title should be returned after page has been unloaded");
+          browser.tabs.get(unloadedTabId, unloadedtab => {
+            browser.test.assertEq("Dummy test page", unloadedtab.title, "Title should be returned after page has been unloaded");
+          });
 
-      await browser.tabs.remove([tab.id, unloadedTabId]);
-      browser.test.notifyPass("tabs.hasCorrectTabTitle");
-    } catch (e) {
-      browser.test.fail(`${e} :: ${e.stack}`);
-      browser.test.notifyFail("tabs.hasCorrectTabTitle");
-    }
+          browser.tabs.remove([tab.id, unloadedTabId]);
+          browser.test.notifyPass("tabs.hasCorrectTabTitle");
+        });
+      }).catch(e => {
+        browser.test.fail(`${e} :: ${e.stack}`);
+        browser.test.notifyFail("tabs.hasCorrectTabTitle");
+      });
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["tabs"],
     },
 
     background,

--- a/browser/components/extensions/test/browser/browser_ext_tabs_events.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_events.js
@@ -1,14 +1,14 @@
 /* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
 /* vim: set sts=2 sw=2 et tw=80: */
 "use strict";
 
 add_task(function* testTabEvents() {
-  async function background() {
+  function background() {
     let events = [];
     browser.tabs.onCreated.addListener(tab => {
       events.push({type: "onCreated", tab});
     });
 
     browser.tabs.onAttached.addListener((tabId, info) => {
       events.push(Object.assign({type: "onAttached", tabId}, info));
     });
@@ -20,131 +20,136 @@ add_task(function* testTabEvents() {
     browser.tabs.onRemoved.addListener((tabId, info) => {
       events.push(Object.assign({type: "onRemoved", tabId}, info));
     });
 
     browser.tabs.onMoved.addListener((tabId, info) => {
       events.push(Object.assign({type: "onMoved", tabId}, info));
     });
 
-    async function expectEvents(names) {
+    function expectEvents(names) {
       browser.test.log(`Expecting events: ${names.join(", ")}`);
 
-      await new Promise(resolve => setTimeout(resolve, 0));
-
-      browser.test.assertEq(names.length, events.length, "Got expected number of events");
-      for (let [i, name] of names.entries()) {
-        browser.test.assertEq(name, i in events && events[i].type,
-                              `Got expected ${name} event`);
-      }
-      return events.splice(0);
+      return new Promise(resolve => {
+        setTimeout(resolve, 0);
+      }).then(() => {
+        browser.test.assertEq(names.length, events.length, "Got expected number of events");
+        for (let [i, name] of names.entries()) {
+          browser.test.assertEq(name, i in events && events[i].type,
+                                `Got expected ${name} event`);
+        }
+        return events.splice(0);
+      });
     }
 
-    try {
-      browser.test.log("Create second browser window");
+    browser.test.log("Create second browser window");
+    let windowId;
+    Promise.all([
+      browser.windows.getCurrent(),
+      browser.windows.create({url: "about:blank"}),
+    ]).then(windows => {
+      windowId = windows[0].id;
+      let otherWindowId = windows[1].id;
+      let initialTab;
 
-      let windows = await Promise.all([
-        browser.windows.getCurrent(),
-        browser.windows.create({url: "about:blank"}),
-      ]);
-
-      let windowId = windows[0].id;
-      let otherWindowId = windows[1].id;
-
-      let [created] = await expectEvents(["onCreated"]);
-      let initialTab = created.tab;
-
+      return expectEvents(["onCreated"]).then(([created]) => {
+        initialTab = created.tab;
 
-      browser.test.log("Create tab in window 1");
-      let tab = await browser.tabs.create({windowId, index: 0, url: "about:blank"});
-      let oldIndex = tab.index;
-      browser.test.assertEq(0, oldIndex, "Tab has the expected index");
-
-      [created] = await expectEvents(["onCreated"]);
-      browser.test.assertEq(tab.id, created.tab.id, "Got expected tab ID");
-      browser.test.assertEq(oldIndex, created.tab.index, "Got expected tab index");
-
+        browser.test.log("Create tab in window 1");
+        return browser.tabs.create({windowId, index: 0, url: "about:blank"});
+      }).then(tab => {
+        let oldIndex = tab.index;
+        browser.test.assertEq(0, oldIndex, "Tab has the expected index");
 
-      browser.test.log("Move tab to window 2");
-      await browser.tabs.move([tab.id], {windowId: otherWindowId, index: 0});
+        return expectEvents(["onCreated"]).then(([created]) => {
+          browser.test.assertEq(tab.id, created.tab.id, "Got expected tab ID");
+          browser.test.assertEq(oldIndex, created.tab.index, "Got expected tab index");
 
-      let [detached, attached] = await expectEvents(["onDetached", "onAttached"]);
-      browser.test.assertEq(oldIndex, detached.oldPosition, "Expected old index");
-      browser.test.assertEq(windowId, detached.oldWindowId, "Expected old window ID");
-
-      browser.test.assertEq(0, attached.newPosition, "Expected new index");
-      browser.test.assertEq(otherWindowId, attached.newWindowId, "Expected new window ID");
-
+          browser.test.log("Move tab to window 2");
+          return browser.tabs.move([tab.id], {windowId: otherWindowId, index: 0});
+        }).then(() => {
+          return expectEvents(["onDetached", "onAttached"]);
+        }).then(([detached, attached]) => {
+          browser.test.assertEq(oldIndex, detached.oldPosition, "Expected old index");
+          browser.test.assertEq(windowId, detached.oldWindowId, "Expected old window ID");
 
-      browser.test.log("Move tab within the same window");
-      let [moved] = await browser.tabs.move([tab.id], {index: 1});
-      browser.test.assertEq(1, moved.index, "Expected new index");
-
-      [moved] = await expectEvents(["onMoved"]);
-      browser.test.assertEq(tab.id, moved.tabId, "Expected tab ID");
-      browser.test.assertEq(0, moved.fromIndex, "Expected old index");
-      browser.test.assertEq(1, moved.toIndex, "Expected new index");
-      browser.test.assertEq(otherWindowId, moved.windowId, "Expected window ID");
+          browser.test.assertEq(0, attached.newPosition, "Expected new index");
+          browser.test.assertEq(otherWindowId, attached.newWindowId, "Expected new window ID");
 
-
-      browser.test.log("Remove tab");
-      await browser.tabs.remove(tab.id);
-      let [removed] = await expectEvents(["onRemoved"]);
+          browser.test.log("Move tab within the same window");
+          return browser.tabs.move([tab.id], {index: 1});
+        }).then(([moved]) => {
+          browser.test.assertEq(1, moved.index, "Expected new index");
 
-      browser.test.assertEq(tab.id, removed.tabId, "Expected removed tab ID");
-      browser.test.assertEq(otherWindowId, removed.windowId, "Expected removed tab window ID");
-      // Note: We want to test for the actual boolean value false here.
-      browser.test.assertEq(false, removed.isWindowClosing, "Expected isWindowClosing value");
-
+          return expectEvents(["onMoved"]);
+        }).then(([moved]) => {
+          browser.test.assertEq(tab.id, moved.tabId, "Expected tab ID");
+          browser.test.assertEq(0, moved.fromIndex, "Expected old index");
+          browser.test.assertEq(1, moved.toIndex, "Expected new index");
+          browser.test.assertEq(otherWindowId, moved.windowId, "Expected window ID");
 
-      browser.test.log("Close second window");
-      await browser.windows.remove(otherWindowId);
-      [removed] = await expectEvents(["onRemoved"]);
-      browser.test.assertEq(initialTab.id, removed.tabId, "Expected removed tab ID");
-      browser.test.assertEq(otherWindowId, removed.windowId, "Expected removed tab window ID");
-      browser.test.assertEq(true, removed.isWindowClosing, "Expected isWindowClosing value");
-
+          browser.test.log("Remove tab");
+          return browser.tabs.remove(tab.id);
+        }).then(() => {
+          return expectEvents(["onRemoved"]);
+        }).then(([removed]) => {
+          browser.test.assertEq(tab.id, removed.tabId, "Expected removed tab ID");
+          browser.test.assertEq(otherWindowId, removed.windowId, "Expected removed tab window ID");
+          // Note: We want to test for the actual boolean value false here.
+          browser.test.assertEq(false, removed.isWindowClosing, "Expected isWindowClosing value");
 
-      browser.test.log("Create additional tab in window 1");
-      tab = await browser.tabs.create({windowId, url: "about:blank"});
-      await expectEvents(["onCreated"]);
-
-
-      browser.test.log("Create a new window, adopting the new tab");
-      // We have to explicitly wait for the event here, since its timing is
-      // not predictable.
-      let promiseAttached = new Promise(resolve => {
-        browser.tabs.onAttached.addListener(function listener(tabId) {
-          browser.tabs.onAttached.removeListener(listener);
-          resolve();
+          browser.test.log("Close second window");
+          return browser.windows.remove(otherWindowId);
+        }).then(() => {
+          return expectEvents(["onRemoved"]);
+        }).then(([removed]) => {
+          browser.test.assertEq(initialTab.id, removed.tabId, "Expected removed tab ID");
+          browser.test.assertEq(otherWindowId, removed.windowId, "Expected removed tab window ID");
+          browser.test.assertEq(true, removed.isWindowClosing, "Expected isWindowClosing value");
         });
       });
+    }).then(() => {
+      browser.test.log("Create additional tab in window 1");
+      return browser.tabs.create({windowId, url: "about:blank"});
+    }).then(tab => {
+      return expectEvents(["onCreated"]).then(() => {
+        browser.test.log("Create a new window, adopting the new tab");
 
-      let [window] = await Promise.all([
-        browser.windows.create({tabId: tab.id}),
-        promiseAttached,
-      ]);
-
-      [detached, attached] = await expectEvents(["onDetached", "onAttached"]);
-
-      browser.test.assertEq(tab.id, detached.tabId, "Expected onDetached tab ID");
+        // We have to explicitly wait for the event here, since its timing is
+        // not predictable.
+        let promiseAttached = new Promise(resolve => {
+          browser.tabs.onAttached.addListener(function listener(tabId) {
+            browser.tabs.onAttached.removeListener(listener);
+            resolve();
+          });
+        });
 
-      browser.test.assertEq(tab.id, attached.tabId, "Expected onAttached tab ID");
-      browser.test.assertEq(0, attached.newPosition, "Expected onAttached new index");
-      browser.test.assertEq(window.id, attached.newWindowId,
-                            "Expected onAttached new window id");
+        return Promise.all([
+          browser.windows.create({tabId: tab.id}),
+          promiseAttached,
+        ]);
+      }).then(([window]) => {
+        return expectEvents(["onDetached", "onAttached"]).then(([detached, attached]) => {
+          browser.test.assertEq(tab.id, detached.tabId, "Expected onDetached tab ID");
 
-      browser.test.log("Close the new window");
-      await browser.windows.remove(window.id);
+          browser.test.assertEq(tab.id, attached.tabId, "Expected onAttached tab ID");
+          browser.test.assertEq(0, attached.newPosition, "Expected onAttached new index");
+          browser.test.assertEq(window.id, attached.newWindowId,
+                                "Expected onAttached new window id");
 
+          browser.test.log("Close the new window");
+          return browser.windows.remove(window.id);
+        });
+      });
+    }).then(() => {
       browser.test.notifyPass("tabs-events");
-    } catch (e) {
+    }).catch(e => {
       browser.test.fail(`${e} :: ${e.stack}`);
       browser.test.notifyFail("tabs-events");
-    }
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["tabs"],
     },
 
     background,
@@ -166,24 +171,26 @@ add_task(function* testTabEventsSize() {
     });
 
     browser.tabs.onUpdated.addListener((tabId, changeInfo, tab) => {
       if (changeInfo.status == "complete") {
         sendSizeMessages(tab, "on-updated");
       }
     });
 
-    browser.test.onMessage.addListener(async (msg, arg) => {
+    browser.test.onMessage.addListener((msg, arg) => {
       if (msg === "create-tab") {
-        let tab = await browser.tabs.create({url: "http://example.com/"});
-        sendSizeMessages(tab, "create");
-        browser.test.sendMessage("created-tab-id", tab.id);
+        browser.tabs.create({url: "http://example.com/"}).then(tab => {
+          sendSizeMessages(tab, "create");
+          browser.test.sendMessage("created-tab-id", tab.id);
+        });
       } else if (msg === "update-tab") {
-        let tab = await browser.tabs.update(arg, {url: "http://example.org/"});
-        sendSizeMessages(tab, "update");
+        browser.tabs.update(arg, {url: "http://example.org/"}).then(tab => {
+          sendSizeMessages(tab, "update");
+        });
       } else if (msg === "remove-tab") {
         browser.tabs.remove(arg);
         browser.test.sendMessage("tab-removed");
       }
     });
 
     browser.test.sendMessage("ready");
   }
@@ -226,17 +233,19 @@ add_task(function* testTabEventsSize() {
     yield extension.awaitMessage("tab-removed");
   }
 
   yield extension.unload();
   SpecialPowers.clearUserPref(RESOLUTION_PREF);
 });
 
 add_task(function* testTabRemovalEvent() {
-  async function background() {
+  function background() {
+    let removalTabId;
+
     function awaitLoad(tabId) {
       return new Promise(resolve => {
         browser.tabs.onUpdated.addListener(function listener(tabId_, changed, tab) {
           if (tabId == tabId_ && changed.status == "complete") {
             browser.tabs.onUpdated.removeListener(listener);
             resolve();
           }
         });
@@ -248,26 +257,27 @@ add_task(function* testTabRemovalEvent()
       chrome.tabs.query({}, tabs => {
         for (let tab of tabs) {
           browser.test.assertTrue(tab.id != tabId, "Tab query should not include removed tabId");
         }
         browser.test.notifyPass("tabs-events");
       });
     });
 
-    try {
-      let url = "http://example.com/browser/browser/components/extensions/test/browser/context.html";
-      let tab = await browser.tabs.create({url: url});
-      await awaitLoad(tab.id);
-
-      await browser.tabs.remove(tab.id);
-    } catch (e) {
+    let url = "http://example.com/browser/browser/components/extensions/test/browser/context.html";
+    browser.tabs.create({url: url})
+    .then(tab => {
+      removalTabId = tab.id;
+      return awaitLoad(tab.id);
+    }).then(() => {
+      return browser.tabs.remove(removalTabId);
+    }).catch(e => {
       browser.test.fail(`${e} :: ${e.stack}`);
       browser.test.notifyFail("tabs-events");
-    }
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["tabs"],
     },
 
     background,

--- a/browser/components/extensions/test/browser/browser_ext_tabs_executeScript.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_executeScript.js
@@ -31,23 +31,22 @@ add_task(function* testExecuteScript() {
 
   let messageManagersSize = countMM(MessageChannel.messageManagers);
   let responseManagersSize = countMM(MessageChannel.responseManagers);
 
   const BASE = "http://mochi.test:8888/browser/browser/components/extensions/test/browser/";
   const URL = BASE + "file_iframe_document.html";
   let tab = yield BrowserTestUtils.openNewForegroundTab(gBrowser, URL, true);
 
-  async function background() {
-    try {
-      let [tab] = await browser.tabs.query({active: true, currentWindow: true});
-      let frames = await browser.webNavigation.getAllFrames({tabId: tab.id});
-
+  function background() {
+    browser.tabs.query({active: true, currentWindow: true}).then(tabs => {
+      return browser.webNavigation.getAllFrames({tabId: tabs[0].id});
+    }).then(frames => {
       browser.test.log(`FRAMES: ${frames[1].frameId} ${JSON.stringify(frames)}\n`);
-      await Promise.all([
+      return Promise.all([
         browser.tabs.executeScript({
           code: "42",
         }).then(result => {
           browser.test.assertEq(1, result.length, "Expected one callback result");
           browser.test.assertEq(42, result[0], "Expected callback result");
         }),
 
         browser.tabs.executeScript({
@@ -123,30 +122,30 @@ add_task(function* testExecuteScript() {
           let details = {
             frame_id: Number.MAX_SAFE_INTEGER,
             matchesHost: ["http://mochi.test/", "http://example.com/"],
           };
           browser.test.assertEq(`No window matching ${JSON.stringify(details)}`,
                                 error.message, "Got expected error");
         }),
 
-        browser.tabs.create({url: "http://example.net/", active: false}).then(async tab => {
-          await browser.tabs.executeScript(tab.id, {
+        browser.tabs.create({url: "http://example.net/", active: false}).then(tab => {
+          return browser.tabs.executeScript(tab.id, {
             code: "42",
           }).then(result => {
             browser.test.fail("Expected error when trying to execute on invalid domain");
           }, error => {
             let details = {
               matchesHost: ["http://mochi.test/", "http://example.com/"],
             };
             browser.test.assertEq(`No window matching ${JSON.stringify(details)}`,
                                   error.message, "Got expected error");
+          }).then(() => {
+            return browser.tabs.remove(tab.id);
           });
-
-          await browser.tabs.remove(tab.id);
         }),
 
         browser.tabs.executeScript({
           code: "Promise.resolve(42)",
         }).then(result => {
           browser.test.assertEq(42, result[0], "Got expected promise resolution value as result");
         }),
 
@@ -174,37 +173,37 @@ add_task(function* testExecuteScript() {
         browser.tabs.executeScript({
           code: "location.href;",
           frameId: frames[1].frameId,
         }).then(result => {
           browser.test.assertEq(1, result.length, "Expected one result");
           browser.test.assertEq("http://mochi.test:8888/", result[0], "Result for frameId[1] is correct");
         }),
 
-        browser.tabs.create({url: "http://example.com/"}).then(async tab => {
-          let result = await browser.tabs.executeScript(tab.id, {code: "location.href"});
+        browser.tabs.create({url: "http://example.com/"}).then(tab => {
+          return browser.tabs.executeScript(tab.id, {code: "location.href"}).then(result => {
+            browser.test.assertEq("http://example.com/", result[0], "Script executed correctly in new tab");
 
-          browser.test.assertEq("http://example.com/", result[0], "Script executed correctly in new tab");
-
-          await browser.tabs.remove(tab.id);
+            return browser.tabs.remove(tab.id);
+          });
         }),
 
         new Promise(resolve => {
           browser.runtime.onMessage.addListener(message => {
             browser.test.assertEq("script ran", message, "Expected runtime message");
             resolve();
           });
         }),
       ]);
-
+    }).then(() => {
       browser.test.notifyPass("executeScript");
-    } catch (e) {
+    }).catch(e => {
       browser.test.fail(`Error: ${e} :: ${e.stack}`);
       browser.test.notifyFail("executeScript");
-    }
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["http://mochi.test/", "http://example.com/", "webNavigation"],
     },
 
     background,

--- a/browser/components/extensions/test/browser/browser_ext_tabs_executeScript_bad.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_executeScript_bad.js
@@ -1,16 +1,16 @@
 "use strict";
 
 // This is a pretty terrible hack, but it's the best we can do until we
 // support |executeScript| callbacks and |lastError|.
 function* testHasNoPermission(params) {
   let contentSetup = params.contentSetup || (() => Promise.resolve());
 
-  async function background(contentSetup) {
+  function background(contentSetup) {
     browser.runtime.onMessage.addListener((msg, sender) => {
       browser.test.assertEq(msg, "second script ran", "second script ran");
       browser.test.notifyPass("executeScript");
     });
 
     browser.test.onMessage.addListener(msg => {
       browser.test.assertEq(msg, "execute-script");
 
@@ -25,19 +25,19 @@ function* testHasNoPermission(params) {
         // it, but it's just about the best we can do until we
         // support callbacks for executeScript.
         browser.tabs.executeScript(tabs[1].id, {
           file: "second-script.js",
         });
       });
     });
 
-    await contentSetup();
-
-    browser.test.sendMessage("ready");
+    contentSetup().then(() => {
+      browser.test.sendMessage("ready");
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: params.manifest,
 
     background: `(${background})(${contentSetup})`,
 
     files: {
@@ -127,76 +127,83 @@ add_task(function* testBadPermissions() 
   });
 
   info("Test active tab, page action, no click");
   yield testHasNoPermission({
     manifest: {
       "permissions": ["http://example.com/", "activeTab"],
       "page_action": {},
     },
-    async contentSetup() {
-      let [tab] = await browser.tabs.query({active: true, currentWindow: true});
-      await browser.pageAction.show(tab.id);
+    contentSetup() {
+      return new Promise(resolve => {
+        browser.tabs.query({active: true, currentWindow: true}, tabs => {
+          browser.pageAction.show(tabs[0].id).then(() => {
+            resolve();
+          });
+        });
+      });
     },
   });
 
   yield BrowserTestUtils.removeTab(tab2);
   yield BrowserTestUtils.removeTab(tab1);
 });
 
 add_task(function* testBadURL() {
-  async function background() {
-    let promises = [
-      new Promise(resolve => {
+  function background() {
+    browser.tabs.query({currentWindow: true}, tabs => {
+      let promises = [
+        new Promise(resolve => {
+          browser.tabs.executeScript({
+            file: "http://example.com/script.js",
+          }, result => {
+            browser.test.assertEq(undefined, result, "Result value");
+
+            browser.test.assertTrue(browser.extension.lastError instanceof Error,
+                                    "runtime.lastError is Error");
+
+            browser.test.assertTrue(browser.runtime.lastError instanceof Error,
+                                    "runtime.lastError is Error");
+
+            browser.test.assertEq(
+              "Files to be injected must be within the extension",
+              browser.extension.lastError && browser.extension.lastError.message,
+              "extension.lastError value");
+
+            browser.test.assertEq(
+              "Files to be injected must be within the extension",
+              browser.runtime.lastError && browser.runtime.lastError.message,
+              "runtime.lastError value");
+
+            resolve();
+          });
+        }),
+
         browser.tabs.executeScript({
           file: "http://example.com/script.js",
-        }, result => {
-          browser.test.assertEq(undefined, result, "Result value");
-
-          browser.test.assertTrue(browser.extension.lastError instanceof Error,
-                                  "runtime.lastError is Error");
+        }).catch(error => {
+          browser.test.assertTrue(error instanceof Error, "Error is Error");
 
-          browser.test.assertTrue(browser.runtime.lastError instanceof Error,
-                                  "runtime.lastError is Error");
+          browser.test.assertEq(null, browser.extension.lastError,
+                                "extension.lastError value");
 
-          browser.test.assertEq(
-            "Files to be injected must be within the extension",
-            browser.extension.lastError && browser.extension.lastError.message,
-            "extension.lastError value");
+          browser.test.assertEq(null, browser.runtime.lastError,
+                                "runtime.lastError value");
 
           browser.test.assertEq(
             "Files to be injected must be within the extension",
-            browser.runtime.lastError && browser.runtime.lastError.message,
-            "runtime.lastError value");
-
-          resolve();
-        });
-      }),
-
-      browser.tabs.executeScript({
-        file: "http://example.com/script.js",
-      }).catch(error => {
-        browser.test.assertTrue(error instanceof Error, "Error is Error");
+            error && error.message,
+            "error value");
+        }),
+      ];
 
-        browser.test.assertEq(null, browser.extension.lastError,
-                              "extension.lastError value");
-
-        browser.test.assertEq(null, browser.runtime.lastError,
-                              "runtime.lastError value");
-
-        browser.test.assertEq(
-          "Files to be injected must be within the extension",
-          error && error.message,
-          "error value");
-      }),
-    ];
-
-    await Promise.all(promises);
-
-    browser.test.notifyPass("executeScript-lastError");
+      Promise.all(promises).then(() => {
+        browser.test.notifyPass("executeScript-lastError");
+      });
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["<all_urls>"],
     },
 
     background,

--- a/browser/components/extensions/test/browser/browser_ext_tabs_executeScript_good.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_executeScript_good.js
@@ -2,33 +2,33 @@
 /* vim: set sts=2 sw=2 et tw=80: */
 "use strict";
 
 requestLongerTimeout(2);
 
 function* testHasPermission(params) {
   let contentSetup = params.contentSetup || (() => Promise.resolve());
 
-  async function background(contentSetup) {
+  function background(contentSetup) {
     browser.runtime.onMessage.addListener((msg, sender) => {
       browser.test.assertEq(msg, "script ran", "script ran");
       browser.test.notifyPass("executeScript");
     });
 
     browser.test.onMessage.addListener(msg => {
       browser.test.assertEq(msg, "execute-script");
 
       browser.tabs.executeScript({
         file: "script.js",
       });
     });
 
-    await contentSetup();
-
-    browser.test.sendMessage("ready");
+    contentSetup().then(() => {
+      browser.test.sendMessage("ready");
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: params.manifest,
 
     background: `(${background})(${contentSetup})`,
 
     files: {
@@ -117,46 +117,57 @@ add_task(function* testGoodPermissions()
   });
 
   info("Test activeTab permission with a page action click");
   yield testHasPermission({
     manifest: {
       "permissions": ["activeTab"],
       "page_action": {},
     },
-    contentSetup: async () => {
-      let [tab] = await browser.tabs.query({active: true, currentWindow: true});
-      await browser.pageAction.show(tab.id);
+    contentSetup() {
+      return new Promise(resolve => {
+        browser.tabs.query({active: true, currentWindow: true}, tabs => {
+          browser.pageAction.show(tabs[0].id).then(() => {
+            resolve();
+          });
+        });
+      });
     },
     setup: clickPageAction,
     tearDown: closePageAction,
   });
 
   info("Test activeTab permission with a browser action w/popup click");
   yield testHasPermission({
     manifest: {
       "permissions": ["activeTab"],
       "browser_action": {"default_popup": "_blank.html"},
     },
-    setup: async extension => {
-      await clickBrowserAction(extension);
-      return awaitExtensionPanel(extension, window, "_blank.html");
+    setup: extension => {
+      return clickBrowserAction(extension).then(() => {
+        return awaitExtensionPanel(extension, window, "_blank.html");
+      });
     },
     tearDown: closeBrowserAction,
   });
 
   info("Test activeTab permission with a page action w/popup click");
   yield testHasPermission({
     manifest: {
       "permissions": ["activeTab"],
       "page_action": {"default_popup": "_blank.html"},
     },
-    contentSetup: async () => {
-      let [tab] = await browser.tabs.query({active: true, currentWindow: true});
-      await browser.pageAction.show(tab.id);
+    contentSetup() {
+      return new Promise(resolve => {
+        browser.tabs.query({active: true, currentWindow: true}, tabs => {
+          browser.pageAction.show(tabs[0].id).then(() => {
+            resolve();
+          });
+        });
+      });
     },
     setup: clickPageAction,
     tearDown: closePageAction,
   });
 
   info("Test activeTab permission with a context menu click");
   yield testHasPermission({
     manifest: {

--- a/browser/components/extensions/test/browser/browser_ext_tabs_executeScript_runAt.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_executeScript_runAt.js
@@ -12,86 +12,91 @@
  *
  * And since we can't actually rely on that timing, it retries any attempts that
  * fail to load as early as expected, but don't load at any illegal time.
  */
 
 add_task(function* testExecuteScript() {
   let tab = yield BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank", true);
 
-  async function background() {
+  function background() {
     let tab;
 
     const BASE = "http://mochi.test:8888/browser/browser/components/extensions/test/browser/";
     const URL = BASE + "file_iframe_document.sjs";
 
     const MAX_TRIES = 10;
-
-    try {
-      [tab] = await browser.tabs.query({active: true, currentWindow: true});
+    let tries = 0;
 
-      let success = false;
-      for (let tries = 0; !success && tries < MAX_TRIES; tries++) {
-        let url = `${URL}?r=${Math.random()}`;
+    function again() {
+      if (tries++ == MAX_TRIES) {
+        return Promise.reject(new Error("Max tries exceeded"));
+      }
+
+      let url = `${URL}?r=${Math.random()}`;
 
-        let loadingPromise = new Promise(resolve => {
-          browser.tabs.onUpdated.addListener(function listener(tabId, changed, tab_) {
-            if (tabId == tab.id && changed.status == "loading" && tab_.url == url) {
-              browser.tabs.onUpdated.removeListener(listener);
-              resolve();
-            }
-          });
+      let loadingPromise = new Promise(resolve => {
+        browser.tabs.onUpdated.addListener(function listener(tabId, changed, tab_) {
+          if (tabId == tab.id && changed.status == "loading" && tab_.url == url) {
+            browser.tabs.onUpdated.removeListener(listener);
+            resolve();
+          }
         });
+      });
 
-        // TODO: Test allFrames and frameId.
+      // TODO: Test allFrames and frameId.
 
-        await browser.tabs.update({url});
-        await loadingPromise;
-
-        let states = await Promise.all([
+      return browser.tabs.update({url}).then(() => {
+        return loadingPromise;
+      }).then(() => {
+        return Promise.all([
           // Send the executeScript requests in the reverse order that we expect
           // them to execute in, to avoid them passing only because of timing
           // races.
           browser.tabs.executeScript({
             code: "document.readyState",
             runAt: "document_idle",
           }),
           browser.tabs.executeScript({
             code: "document.readyState",
             runAt: "document_end",
           }),
           browser.tabs.executeScript({
             code: "document.readyState",
             runAt: "document_start",
           }),
         ].reverse());
-
+      }).then(states => {
         browser.test.log(`Got states: ${states}`);
 
         // Make sure that none of our scripts executed earlier than expected,
         // regardless of retries.
         browser.test.assertTrue(states[1] == "interactive" || states[1] == "complete",
                                 `document_end state is valid: ${states[1]}`);
         browser.test.assertTrue(states[2] == "complete",
                                 `document_idle state is valid: ${states[2]}`);
 
         // If we have the earliest valid states for each script, we're done.
         // Otherwise, try again.
-        success = (states[0] == "loading" &&
-                   states[1] == "interactive" &&
-                   states[2] == "complete");
-      }
+        if (states[0] != "loading" || states[1] != "interactive" || states[2] != "complete") {
+          return again();
+        }
+      });
+    }
 
-      browser.test.assertTrue(success, "Got the earliest expected states at least once");
+    browser.tabs.query({active: true, currentWindow: true}).then(tabs => {
+      tab = tabs[0];
 
+      return again();
+    }).then(() => {
       browser.test.notifyPass("executeScript-runAt");
-    } catch (e) {
+    }).catch(e => {
       browser.test.fail(`Error: ${e} :: ${e.stack}`);
       browser.test.notifyFail("executeScript-runAt");
-    }
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["http://mochi.test/", "tabs"],
     },
 
     background,

--- a/browser/components/extensions/test/browser/browser_ext_tabs_insertCSS.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_insertCSS.js
@@ -5,18 +5,18 @@
 add_task(function* testExecuteScript() {
   let {MessageChannel} = Cu.import("resource://gre/modules/MessageChannel.jsm", {});
 
   let messageManagersSize = MessageChannel.messageManagers.size;
   let responseManagersSize = MessageChannel.responseManagers.size;
 
   let tab = yield BrowserTestUtils.openNewForegroundTab(gBrowser, "http://mochi.test:8888/", true);
 
-  async function background() {
-    let tasks = [
+  function background() {
+    let promises = [
       {
         background: "transparent",
         foreground: "rgb(0, 113, 4)",
         promise: () => {
           return browser.tabs.insertCSS({
             file: "file2.css",
           });
         },
@@ -32,35 +32,41 @@ add_task(function* testExecuteScript() {
       },
     ];
 
     function checkCSS() {
       let computedStyle = window.getComputedStyle(document.body);
       return [computedStyle.backgroundColor, computedStyle.color];
     }
 
-    try {
-      for (let {promise, background, foreground} of tasks) {
-        let result = await promise();
+    function next() {
+      if (!promises.length) {
+        return;
+      }
 
+      let {promise, background, foreground} = promises.shift();
+      return promise().then(result => {
         browser.test.assertEq(undefined, result, "Expected callback result");
 
-        [result] = await browser.tabs.executeScript({
+        return browser.tabs.executeScript({
           code: `(${checkCSS})()`,
         });
-
+      }).then(([result]) => {
         browser.test.assertEq(background, result[0], "Expected background color");
         browser.test.assertEq(foreground, result[1], "Expected foreground color");
-      }
+        return next();
+      });
+    }
 
+    next().then(() => {
       browser.test.notifyPass("insertCSS");
-    } catch (e) {
+    }).catch(e => {
       browser.test.fail(`Error: ${e} :: ${e.stack}`);
       browser.test.notifyFailure("insertCSS");
-    }
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["http://mochi.test/"],
     },
 
     background,

--- a/browser/components/extensions/test/browser/browser_ext_tabs_move.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_move.js
@@ -60,32 +60,39 @@ add_task(function* () {
   yield extension.awaitFinish("tabs.move.multiple");
   yield extension.unload();
 
   extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["tabs"],
     },
 
-    async background() {
-      let [, tab] = await browser.tabs.query({lastFocusedWindow: true});
-
-      // Assuming that tab.id of 12345 does not exist.
-      await browser.tabs.move([tab.id, 12345], {index: 0}).then(
+    background: function() {
+      browser.tabs.query(
+        {lastFocusedWindow: true},
         tabs => {
-          browser.test.fail("Promise should not resolve");
-        },
-        e => {
-          browser.test.assertTrue(/Invalid tab/.test(e),
-                                  "Invalid tab should be in error");
+          let tab = tabs[1];
+          // Assuming that tab.id of 12345 does not exist.
+          browser.tabs.move([tab.id, 12345], {index: 0})
+          .then(
+            tabs => { browser.test.fail("Promise should not resolve"); },
+            e => {
+              browser.test.assertTrue(/Invalid tab/.test(e),
+                                      "Invalid tab should be in error");
+            })
+          .then(
+            browser.tabs.query({lastFocusedWindow: true})
+            .then(
+              (tabs) => {
+                browser.test.assertEq(tabs[1].url, tab.url, "should be second tab");
+                browser.test.notifyPass("tabs.move.invalid");
+              }
+            )
+          );
         });
-
-      let tabs = await browser.tabs.query({lastFocusedWindow: true});
-      browser.test.assertEq(tabs[1].url, tab.url, "should be second tab");
-      browser.test.notifyPass("tabs.move.invalid");
     },
   });
 
   yield extension.startup();
   yield extension.awaitFinish("tabs.move.invalid");
   yield extension.unload();
 
   extension = ExtensionTestUtils.loadExtension({

--- a/browser/components/extensions/test/browser/browser_ext_tabs_move_window.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_move_window.js
@@ -7,37 +7,42 @@ add_task(function* () {
   let window1 = yield BrowserTestUtils.openNewBrowserWindow();
   yield BrowserTestUtils.openNewForegroundTab(window1.gBrowser, "http://example.com/");
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["tabs"],
     },
 
-    async background() {
-      let tabs = await browser.tabs.query({url: "<all_urls>"});
-      let destination = tabs[0];
-      let source = tabs[1]; // skip over about:blank in window1
+    background: function() {
+      browser.tabs.query({
+        url: "<all_urls>",
+      }, function(tabs) {
+        let destination = tabs[0];
+        let source = tabs[1]; // skip over about:blank in window1
+        browser.tabs.move(source.id, {windowId: destination.windowId, index: 0});
 
-      // Assuming that this windowId does not exist.
-      await browser.tabs.move(source.id, {windowId: 123144576, index: 0}).then(
-        tabs => {
-          browser.test.fail("Promise should not resolve");
-        },
-        e => {
-          browser.test.assertTrue(/Invalid window/.test(e),
-                                  "Invalid window should be in error");
-        });
+        browser.tabs.query(
+          {url: "<all_urls>"},
+          tabs => {
+            browser.test.assertEq(tabs[0].url, "http://example.com/");
+            browser.test.assertEq(tabs[0].windowId, destination.windowId);
+            browser.test.notifyPass("tabs.move.window");
+          });
 
-      browser.tabs.move(source.id, {windowId: destination.windowId, index: 0});
-
-      tabs = await browser.tabs.query({url: "<all_urls>"});
-      browser.test.assertEq(tabs[0].url, "http://example.com/");
-      browser.test.assertEq(tabs[0].windowId, destination.windowId);
-      browser.test.notifyPass("tabs.move.window");
+        // Assuming that this windowId does not exist.
+        browser.tabs.move(source.id, {windowId: 123144576, index: 0})
+        .then(
+          tabs => { browser.test.fail("Promise should not resolve"); },
+          e => {
+            browser.test.assertTrue(/Invalid window/.test(e),
+                                    "Invalid window should be in error");
+          }
+        );
+      });
     },
   });
 
   yield extension.startup();
   yield extension.awaitFinish("tabs.move.window");
   yield extension.unload();
 
   for (let tab of window.gBrowser.tabs) {
@@ -56,33 +61,33 @@ add_task(function* test_currentWindowAft
             browser.test.sendMessage("id", win.id);
           });
         }
       });
       browser.test.sendMessage("ready");
     },
   };
 
-  async function background() {
+  function background() {
     let tabId;
-
     const url = browser.extension.getURL("current.html");
-
-    browser.test.onMessage.addListener(async msg => {
+    browser.tabs.create({url}).then(tab => {
+      tabId = tab.id;
+    });
+    browser.test.onMessage.addListener(msg => {
       if (msg === "move") {
-        await browser.windows.create({tabId});
-        browser.test.sendMessage("moved");
+        browser.windows.create({tabId}).then(() => {
+          browser.test.sendMessage("moved");
+        });
       } else if (msg === "close") {
-        await browser.tabs.remove(tabId);
-        browser.test.sendMessage("done");
+        browser.tabs.remove(tabId).then(() => {
+          browser.test.sendMessage("done");
+        });
       }
     });
-
-    let tab = await browser.tabs.create({url});
-    tabId = tab.id;
   }
 
   const extension = ExtensionTestUtils.loadExtension({files, background});
 
   yield extension.startup();
   yield extension.awaitMessage("ready");
 
   extension.sendMessage("current");

--- a/browser/components/extensions/test/browser/browser_ext_tabs_onHighlighted.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_onHighlighted.js
@@ -1,14 +1,14 @@
 /* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
 /* vim: set sts=2 sw=2 et tw=80: */
 "use strict";
 
 add_task(function* testTabEvents() {
-  async function background() {
+  function background() {
     /** The list of active tab ID's */
     let tabIds = [];
 
     /**
      * Stores the events that fire for each tab.
      *
      * events {
      *   tabId1: [event1, event2, ...],
@@ -34,87 +34,89 @@ add_task(function* testTabEvents() {
     });
 
     /**
      * Asserts that the expected events are fired for the tab with id = tabId.
      * The events associated to the specified tab are removed after this check is made.
      *
      * @param {number} tabId
      * @param {Array<string>} expectedEvents
+     * @returns {Promise}
      */
-    async function expectEvents(tabId, expectedEvents) {
+    function expectEvents(tabId, expectedEvents) {
       browser.test.log(`Expecting events: ${expectedEvents.join(", ")}`);
 
-      await new Promise(resolve => setTimeout(resolve, 0));
-
-      browser.test.assertEq(expectedEvents.length, events[tabId].length,
-                            `Got expected number of events for ${tabId}`);
-
-      for (let [i, name] of expectedEvents.entries()) {
-        browser.test.assertEq(name, i in events[tabId] && events[tabId][i],
-                              `Got expected ${name} event`);
-      }
-      delete events[tabId];
+      return new Promise(resolve => {
+        setTimeout(resolve, 0);
+      }).then(() => {
+        browser.test.assertEq(expectedEvents.length, events[tabId].length,
+         `Got expected number of events for ${tabId}`);
+        for (let [i, name] of expectedEvents.entries()) {
+          browser.test.assertEq(name, i in events[tabId] && events[tabId][i],
+                                `Got expected ${name} event`);
+        }
+        delete events[tabId];
+      });
     }
 
     /**
      * Opens a new tab and asserts that the correct events are fired.
      *
      * @param {number} windowId
+     * @returns {Promise}
      */
-    async function openTab(windowId) {
-      let tab = await browser.tabs.create({windowId});
-
-      tabIds.push(tab.id);
-      browser.test.log(`Opened tab ${tab.id}`);
-
-      await expectEvents(tab.id, [
-        "onActivated",
-        "onHighlighted",
-      ]);
+    function openTab(windowId) {
+      return browser.tabs.create({windowId}).then(tab => {
+        tabIds.push(tab.id);
+        browser.test.log(`Opened tab ${tab.id}`);
+        return expectEvents(tab.id, [
+          "onActivated",
+          "onHighlighted",
+        ]);
+      });
     }
 
     /**
      * Highlights an existing tab and asserts that the correct events are fired.
      *
      * @param {number} tabId
+     * @returns {Promise}
      */
-    async function highlightTab(tabId) {
+    function highlightTab(tabId) {
       browser.test.log(`Highlighting tab ${tabId}`);
-      let tab = await browser.tabs.update(tabId, {active: true});
-
-      browser.test.assertEq(tab.id, tabId, `Tab ${tab.id} highlighted`);
-
-      await expectEvents(tab.id, [
-        "onActivated",
-        "onHighlighted",
-      ]);
+      return browser.tabs.update(tabId, {active: true}).then(tab => {
+        browser.test.assertEq(tab.id, tabId, `Tab ${tab.id} highlighted`);
+        return expectEvents(tab.id, [
+          "onActivated",
+          "onHighlighted",
+        ]);
+      });
     }
 
     /**
      * The main entry point to the tests.
      */
-    let tabs = await browser.tabs.query({active: true, currentWindow: true});
-
-    let activeWindow = tabs[0].windowId;
-    await Promise.all([
-      openTab(activeWindow),
-      openTab(activeWindow),
-      openTab(activeWindow),
-    ]);
-
-    await Promise.all([
-      highlightTab(tabIds[0]),
-      highlightTab(tabIds[1]),
-      highlightTab(tabIds[2]),
-    ]);
-
-    await Promise.all(tabIds.map(id => browser.tabs.remove(id)));
-
-    browser.test.notifyPass("tabs.highlight");
+    browser.tabs.query({active: true, currentWindow: true}, tabs => {
+      let activeWindow = tabs[0].windowId;
+      Promise.all([
+        openTab(activeWindow),
+        openTab(activeWindow),
+        openTab(activeWindow),
+      ]).then(() => {
+        return Promise.all([
+          highlightTab(tabIds[0]),
+          highlightTab(tabIds[1]),
+          highlightTab(tabIds[2]),
+        ]);
+      }).then(() => {
+        return Promise.all(tabIds.map(id => browser.tabs.remove(id)));
+      }).then(() => {
+        browser.test.notifyPass("tabs.highlight");
+      });
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["tabs"],
     },
 
     background,

--- a/browser/components/extensions/test/browser/browser_ext_tabs_query.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_query.js
@@ -134,21 +134,21 @@ add_task(function* () {
 
   // test width and height
   extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": ["tabs"],
     },
 
     background: function() {
-      browser.test.onMessage.addListener(async msg => {
-        let tabs = await browser.tabs.query({active: true});
-
-        browser.test.assertEq(tabs.length, 1, "should have one tab");
-        browser.test.sendMessage("dims", {width: tabs[0].width, height: tabs[0].height});
+      browser.test.onMessage.addListener((msg) => {
+        browser.tabs.query({active: true}).then(tabs => {
+          browser.test.assertEq(tabs.length, 1, "should have one tab");
+          browser.test.sendMessage("dims", {width: tabs[0].width, height: tabs[0].height});
+        });
       });
       browser.test.sendMessage("ready");
     },
   });
 
   const RESOLUTION_PREF = "layout.css.devPixelsPerPx";
   registerCleanupFunction(() => {
     SpecialPowers.clearUserPref(RESOLUTION_PREF);
@@ -177,41 +177,40 @@ add_task(function* () {
 });
 
 add_task(function* testQueryPermissions() {
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": [],
     },
 
-    async background() {
-      try {
-        let tabs = await browser.tabs.query({currentWindow: true, active: true});
+    background: function(x) {
+      browser.tabs.query({currentWindow: true, active: true}).then((tabs) => {
         browser.test.assertEq(tabs.length, 1, "Expect query to return tabs");
         browser.test.notifyPass("queryPermissions");
-      } catch (e) {
+      }).catch((e) => {
         browser.test.notifyFail("queryPermissions");
-      }
+      });
     },
   });
 
   yield extension.startup();
 
   yield extension.awaitFinish("queryPermissions");
 
   yield extension.unload();
 });
 
 add_task(function* testQueryWithURLPermissions() {
   let extension = ExtensionTestUtils.loadExtension({
     manifest: {
       "permissions": [],
     },
 
-    background: function() {
+    background: function(x) {
       browser.tabs.query({"url": "http://www.bbc.com/"}).then(() => {
         browser.test.notifyFail("queryWithURLPermissions");
       }).catch((e) => {
         browser.test.assertEq('The "tabs" permission is required to use the query API with the "url" parameter',
                               e.message, "Expected permissions error message");
         browser.test.notifyPass("queryWithURLPermissions");
       });
     },

--- a/browser/components/extensions/test/browser/browser_ext_tabs_reload.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_reload.js
@@ -14,41 +14,41 @@ add_task(function* () {
       },
       "tab.html":
         `<head>
           <meta charset="utf-8">
           <script src="tab.js"></script>
         </head>`,
     },
 
-    async background() {
+    background: function() {
       let tabLoadedCount = 0;
 
-      let tab = await browser.tabs.create({url: "tab.html", active: true});
+      browser.tabs.create({url: "tab.html", active: true}).then(tab => {
+        browser.runtime.onMessage.addListener(msg => {
+          if (msg == "tab-loaded") {
+            tabLoadedCount++;
 
-      browser.runtime.onMessage.addListener(msg => {
-        if (msg == "tab-loaded") {
-          tabLoadedCount++;
-
-          if (tabLoadedCount == 1) {
-            // Reload the tab once passing no arguments.
-            return browser.tabs.reload();
-          }
+            if (tabLoadedCount == 1) {
+              // Reload the tab once passing no arguments.
+              return browser.tabs.reload();
+            }
 
-          if (tabLoadedCount == 2) {
-            // Reload the tab again with explicit arguments.
-            return browser.tabs.reload(tab.id, {
-              bypassCache: false,
-            });
+            if (tabLoadedCount == 2) {
+              // Reload the tab again with explicit arguments.
+              return browser.tabs.reload(tab.id, {
+                bypassCache: false,
+              });
+            }
+
+            if (tabLoadedCount == 3) {
+              browser.test.notifyPass("tabs.reload");
+            }
           }
-
-          if (tabLoadedCount == 3) {
-            browser.test.notifyPass("tabs.reload");
-          }
-        }
+        });
       });
     },
   });
 
   yield extension.startup();
   yield extension.awaitFinish("tabs.reload");
   yield extension.unload();
 });