--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -157,17 +157,16 @@ pref("app.update.service.enabled", true)
 //  .. etc ..
 //
 pref("extensions.update.enabled", true);
 pref("extensions.update.url", "https://versioncheck.addons.mozilla.org/update/VersionCheck.php?reqVersion=%REQ_VERSION%&id=%ITEM_ID%&version=%ITEM_VERSION%&maxAppVersion=%ITEM_MAXAPPVERSION%&status=%ITEM_STATUS%&appID=%APP_ID%&appVersion=%APP_VERSION%&appOS=%APP_OS%&appABI=%APP_ABI%&locale=%APP_LOCALE%&currentAppVersion=%CURRENT_APP_VERSION%&updateType=%UPDATE_TYPE%&compatMode=%COMPATIBILITY_MODE%");
 pref("extensions.update.background.url", "https://versioncheck-bg.addons.mozilla.org/update/VersionCheck.php?reqVersion=%REQ_VERSION%&id=%ITEM_ID%&version=%ITEM_VERSION%&maxAppVersion=%ITEM_MAXAPPVERSION%&status=%ITEM_STATUS%&appID=%APP_ID%&appVersion=%APP_VERSION%&appOS=%APP_OS%&appABI=%APP_ABI%&locale=%APP_LOCALE%&currentAppVersion=%CURRENT_APP_VERSION%&updateType=%UPDATE_TYPE%&compatMode=%COMPATIBILITY_MODE%");
 pref("extensions.update.interval", 86400);  // Check for updates to Extensions and
                                             // Themes every day
 // Non-symmetric (not shared by extensions) extension-specific [update] preferences
-pref("extensions.dss.enabled", false);          // Dynamic Skin Switching
 pref("extensions.dss.switchPending", false);    // Non-dynamic switch pending after next
                                                 // restart.
 
 pref("extensions.{972ce4c6-7e08-4474-a285-3208198ce6fd}.name", "chrome://browser/locale/browser.properties");
 pref("extensions.{972ce4c6-7e08-4474-a285-3208198ce6fd}.description", "chrome://browser/locale/browser.properties");
 
 pref("extensions.webextensions.themes.icons.buttons", "back,forward,reload,stop,bookmark_star,bookmark_menu,downloads,home,app_menu,cut,copy,paste,new_window,new_private_window,save_page,print,history,full_screen,find,options,addons,developer,synced_tabs,open_file,sidebars,share_page,subscribe,text_encoding,email_link,forget,pocket");
 

--- a/browser/base/content/test/general/browser_bug592338.js
+++ b/browser/base/content/test/general/browser_bug592338.js
@@ -72,64 +72,54 @@ function test_install_lwtheme() {
   });
 },
 
 function test_lwtheme_switch_theme() {
   is(LightweightThemeManager.currentTheme, null, "Should be no lightweight theme selected");
 
   AddonManager.getAddonByID("theme-xpi@tests.mozilla.org", function(aAddon) {
     aAddon.userDisabled = false;
-    ok(aAddon.isActive, "Theme should have immediately enabled");
-    Services.prefs.setBoolPref("extensions.dss.enabled", false);
+    ok(!aAddon.isActive, "Theme shouldn't have immediately enabled");
 
     var pm = Services.perms;
     pm.add(makeURI("https://example.com/"), "install", pm.ALLOW_ACTION);
 
     gBrowser.selectedTab = gBrowser.addTab("https://example.com/browser/browser/base/content/test/general/bug592338.html");
     gBrowser.selectedBrowser.addEventListener("pageshow", function() {
       if (gBrowser.contentDocument.location.href == "about:blank")
         return;
 
-      gBrowser.selectedBrowser.removeEventListener("pageshow", arguments.callee);
+      executeSoon(function() {
+        is(LightweightThemeManager.currentTheme, null, "Should not have installed the test lwtheme");
+        ok(!aAddon.isActive, "Test theme should still not be active");
+        ok(!aAddon.userDisabled, "Test theme should not be disabled yet");
 
-      executeSoon(function() {
-        wait_for_notification(function(aPanel) {
-          is(LightweightThemeManager.currentTheme, null, "Should not have installed the test lwtheme");
-          ok(aAddon.isActive, "Test theme should still be active");
-
-          let notification = aPanel.childNodes[0];
-          is(notification.button.label, "Restart Now", "Should have seen the right button");
+        aAddon.userDisabled = true;
 
-          ok(aAddon.userDisabled, "Should be waiting to disable the test theme");
-          aAddon.userDisabled = false;
-          Services.prefs.setBoolPref("extensions.dss.enabled", true);
+        gBrowser.removeTab(gBrowser.selectedTab);
 
-          gBrowser.removeTab(gBrowser.selectedTab);
+        Services.perms.remove(makeURI("http://example.com"), "install");
 
-          Services.perms.remove(makeURI("http://example.com"), "install");
-
-          runNextTest();
-        });
-        BrowserTestUtils.synthesizeMouse("#theme-install", 2, 2, {}, gBrowser.selectedBrowser);
+        runNextTest();
       });
-    });
+      BrowserTestUtils.synthesizeMouse("#theme-install", 2, 2, {}, gBrowser.selectedBrowser);
+    }, { once: true });
   });
 }
 ];
 
 function runNextTest() {
   AddonManager.getAllInstalls(function(aInstalls) {
     is(aInstalls.length, 0, "Should be no active installs");
 
     if (TESTS.length == 0) {
       AddonManager.getAddonByID("theme-xpi@tests.mozilla.org", function(aAddon) {
         aAddon.uninstall();
 
         Services.prefs.setBoolPref("extensions.logging.enabled", false);
-        Services.prefs.setBoolPref("extensions.dss.enabled", false);
 
         finish();
       });
       return;
     }
 
     info("Running " + TESTS[0].name);
     TESTS.shift()();
@@ -142,21 +132,16 @@ function test() {
   Services.prefs.setBoolPref("extensions.logging.enabled", true);
 
   AddonManager.getInstallForURL(TESTROOT + "theme.xpi", function(aInstall) {
     aInstall.addListener({
       onInstallEnded() {
         AddonManager.getAddonByID("theme-xpi@tests.mozilla.org", function(aAddon) {
           isnot(aAddon, null, "Should have installed the test theme.");
 
-          // In order to switch themes while the test is running we turn on dynamic
-          // theme switching. This means the test isn't exactly correct but should
-          // do some good
-          Services.prefs.setBoolPref("extensions.dss.enabled", true);
-
           runNextTest();
         });
       }
     });
 
     aInstall.install();
   }, "application/x-xpinstall");
 }

--- a/toolkit/mozapps/extensions/LightweightThemeManager.jsm
+++ b/toolkit/mozapps/extensions/LightweightThemeManager.jsm
@@ -12,17 +12,16 @@ const Ci = Components.interfaces;
 Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
 Components.utils.import("resource://gre/modules/AddonManager.jsm");
 /* globals AddonManagerPrivate*/
 Components.utils.import("resource://gre/modules/Services.jsm");
 
 const ID_SUFFIX              = "@personas.mozilla.org";
 const PREF_LWTHEME_TO_SELECT = "extensions.lwThemeToSelect";
 const PREF_GENERAL_SKINS_SELECTEDSKIN = "general.skins.selectedSkin";
-const PREF_EM_DSS_ENABLED    = "extensions.dss.enabled";
 const ADDON_TYPE             = "theme";
 const ADDON_TYPE_WEBEXT      = "webextension-theme";
 
 const URI_EXTENSION_STRINGS  = "chrome://mozapps/locale/extensions/extensions.properties";
 
 const STRING_TYPE_NAME       = "type.%ID%.name";
 
 const DEFAULT_MAX_USED_THEMES_COUNT = 30;
@@ -496,25 +495,18 @@ AddonWrapper.prototype = {
     if (this.isActive == this.userDisabled)
       pending |= this.isActive ? AddonManager.PENDING_DISABLE : AddonManager.PENDING_ENABLE;
     return pending;
   },
 
   get operationsRequiringRestart() {
     // If a non-default theme is in use then a restart will be required to
     // enable lightweight themes unless dynamic theme switching is enabled
-    if (Services.prefs.prefHasUserValue(PREF_GENERAL_SKINS_SELECTEDSKIN)) {
-      try {
-        if (Services.prefs.getBoolPref(PREF_EM_DSS_ENABLED))
-          return AddonManager.OP_NEEDS_RESTART_NONE;
-      } catch (e) {
-      }
+    if (Services.prefs.prefHasUserValue(PREF_GENERAL_SKINS_SELECTEDSKIN))
       return AddonManager.OP_NEEDS_RESTART_ENABLE;
-    }
-
     return AddonManager.OP_NEEDS_RESTART_NONE;
   },
 
   get size() {
     // The size changes depending on whether the theme is in use or not, this is
     // probably not worth exposing.
     return null;
   },

--- a/toolkit/mozapps/extensions/internal/XPIProvider.jsm
+++ b/toolkit/mozapps/extensions/internal/XPIProvider.jsm
@@ -98,19 +98,18 @@ Cu.importGlobalProperties(["URL"]);
 const nsIFile = Components.Constructor("@mozilla.org/file/local;1", "nsIFile",
                                        "initWithPath");
 
 const PREF_DB_SCHEMA                  = "extensions.databaseSchema";
 const PREF_INSTALL_CACHE              = "extensions.installCache";
 const PREF_XPI_STATE                  = "extensions.xpiState";
 const PREF_BOOTSTRAP_ADDONS           = "extensions.bootstrappedAddons";
 const PREF_PENDING_OPERATIONS         = "extensions.pendingOperations";
-const PREF_EM_DSS_ENABLED             = "extensions.dss.enabled";
-const PREF_DSS_SWITCHPENDING          = "extensions.dss.switchPending";
-const PREF_DSS_SKIN_TO_SELECT         = "extensions.lastSelectedSkin";
+const PREF_SKIN_SWITCHPENDING         = "extensions.dss.switchPending";
+const PREF_SKIN_TO_SELECT             = "extensions.lastSelectedSkin";
 const PREF_GENERAL_SKINS_SELECTEDSKIN = "general.skins.selectedSkin";
 const PREF_EM_UPDATE_URL              = "extensions.update.url";
 const PREF_EM_UPDATE_BACKGROUND_URL   = "extensions.update.background.url";
 const PREF_EM_ENABLED_ADDONS          = "extensions.enabledAddons";
 const PREF_EM_EXTENSION_FORMAT        = "extensions.";
 const PREF_EM_ENABLED_SCOPES          = "extensions.enabledScopes";
 const PREF_EM_SHOW_MISMATCH_UI        = "extensions.showMismatchUI";
 const PREF_XPI_ENABLED                = "xpinstall.enabled";
@@ -3008,31 +3007,31 @@ this.XPIProvider = {
     Services.obs.notifyObservers(null, "xpi-provider-shutdown", null);
     return undefined;
   },
 
   /**
    * Applies any pending theme change to the preferences.
    */
   applyThemeChange() {
-    if (!Preferences.get(PREF_DSS_SWITCHPENDING, false))
+    if (!Preferences.get(PREF_SKIN_SWITCHPENDING, false))
       return;
 
     // Tell the Chrome Registry which Skin to select
     try {
-      this.selectedSkin = Preferences.get(PREF_DSS_SKIN_TO_SELECT);
+      this.selectedSkin = Preferences.get(PREF_SKIN_TO_SELECT);
       Services.prefs.setCharPref(PREF_GENERAL_SKINS_SELECTEDSKIN,
                                  this.selectedSkin);
-      Services.prefs.clearUserPref(PREF_DSS_SKIN_TO_SELECT);
+      Services.prefs.clearUserPref(PREF_SKIN_TO_SELECT);
       logger.debug("Changed skin to " + this.selectedSkin);
       this.currentSkin = this.selectedSkin;
     } catch (e) {
       logger.error("Error applying theme change", e);
     }
-    Services.prefs.clearUserPref(PREF_DSS_SWITCHPENDING);
+    Services.prefs.clearUserPref(PREF_SKIN_SWITCHPENDING);
   },
 
   /**
    * If the application has been upgraded and there are add-ons outside the
    * application directory then we may need to synchronize compatibility
    * information but only if the mismatch UI isn't disabled.
    *
    * @returns False if no update check is needed, otherwise an array of add-on
@@ -4326,24 +4325,24 @@ this.XPIProvider = {
       } else if (isChangedAddon) {
         newSkin = theme.internalName;
       } else if (theme.userDisabled == false && !theme.pendingUninstall) {
         previousTheme = theme;
       }
     }
 
     if (aPendingRestart) {
-      Services.prefs.setBoolPref(PREF_DSS_SWITCHPENDING, true);
-      Services.prefs.setCharPref(PREF_DSS_SKIN_TO_SELECT, newSkin);
+      Services.prefs.setBoolPref(PREF_SKIN_SWITCHPENDING, true);
+      Services.prefs.setCharPref(PREF_SKIN_TO_SELECT, newSkin);
     } else if (newSkin == this.currentSkin) {
       try {
-        Services.prefs.clearUserPref(PREF_DSS_SWITCHPENDING);
+        Services.prefs.clearUserPref(PREF_SKIN_SWITCHPENDING);
       } catch (e) { }
       try {
-        Services.prefs.clearUserPref(PREF_DSS_SKIN_TO_SELECT);
+        Services.prefs.clearUserPref(PREF_SKIN_TO_SELECT);
       } catch (e) { }
     } else {
       Services.prefs.setCharPref(PREF_GENERAL_SKINS_SELECTEDSKIN, newSkin);
       this.currentSkin = newSkin;
     }
     this.selectedSkin = newSkin;
 
     // Flush the preferences to disk so they don't get out of sync with the
@@ -4413,18 +4412,18 @@ this.XPIProvider = {
         this.updateAddonDisabledState(addon, false);
       } else if (!this.extensionsActive) {
         // During startup we may end up trying to enable the default theme when
         // the database thinks it is already enabled (see f.e. bug 638847). In
         // this case just force the theme preferences to be correct
         Services.prefs.setCharPref(PREF_GENERAL_SKINS_SELECTEDSKIN,
                                    addon.internalName);
         this.currentSkin = this.selectedSkin = addon.internalName;
-        Preferences.reset(PREF_DSS_SKIN_TO_SELECT);
-        Preferences.reset(PREF_DSS_SWITCHPENDING);
+        Preferences.reset(PREF_SKIN_TO_SELECT);
+        Preferences.reset(PREF_SKIN_SWITCHPENDING);
       } else {
         logger.warn("Attempting to activate an already active default theme");
       }
     } else {
       logger.warn("Unable to activate the default theme");
     }
   },
 
@@ -4565,20 +4564,16 @@ this.XPIProvider = {
 
     if (isTheme(aAddon.type)) {
       if (isWebExtension(aAddon.type)) {
         // Enabling a WebExtension type theme requires a restart ONLY when the
         // theme-to-be-disabled requires a restart.
         let theme = XPIDatabase.getVisibleAddonForInternalName(this.currentSkin);
         return !theme || this.disableRequiresRestart(theme);
       }
-      // If dynamic theme switching is enabled then switching themes does not
-      // require a restart
-      if (Preferences.get(PREF_EM_DSS_ENABLED))
-        return false;
 
       // If the theme is already the theme in use then no restart is necessary.
       // This covers the case where the default theme is in use but a
       // lightweight theme is considered active.
       return aAddon.internalName != this.currentSkin;
     }
 
     if (this.e10sBlocksEnabling(aAddon))
@@ -4605,21 +4600,16 @@ this.XPIProvider = {
     if (Services.appinfo.inSafeMode)
       return false;
 
     // Anything that isn't active is already disabled
     if (!aAddon.active)
       return false;
 
     if (aAddon.type == "theme") {
-      // If dynamic theme switching is enabled then switching themes does not
-      // require a restart
-      if (Preferences.get(PREF_EM_DSS_ENABLED))
-        return false;
-
       // Non-default themes always require a restart to disable since it will
       // be switching from one theme to another or to the default theme and a
       // lightweight theme.
       if (aAddon.internalName != this.defaultSkin)
         return true;
 
       // The default theme requires a restart to disable if we are in the
       // process of switching to a different theme. Note that this makes the

--- a/toolkit/mozapps/extensions/internal/XPIProviderUtils.js
+++ b/toolkit/mozapps/extensions/internal/XPIProviderUtils.js
@@ -50,17 +50,16 @@ const FILE_JSON_DB                    = 
 const FILE_OLD_DATABASE               = "extensions.rdf";
 const FILE_XPI_ADDONS_LIST            = "extensions.ini";
 
 // The last version of DB_SCHEMA implemented in SQLITE
 const LAST_SQLITE_DB_SCHEMA           = 14;
 const PREF_DB_SCHEMA                  = "extensions.databaseSchema";
 const PREF_PENDING_OPERATIONS         = "extensions.pendingOperations";
 const PREF_EM_ENABLED_ADDONS          = "extensions.enabledAddons";
-const PREF_EM_DSS_ENABLED             = "extensions.dss.enabled";
 const PREF_EM_AUTO_DISABLED_SCOPES    = "extensions.autoDisableScopes";
 const PREF_E10S_BLOCKED_BY_ADDONS     = "extensions.e10sBlockedByAddons";
 const PREF_E10S_HAS_NONEXEMPT_ADDON   = "extensions.e10s.rollout.hasAddon";
 
 const KEY_APP_PROFILE                 = "app-profile";
 const KEY_APP_SYSTEM_ADDONS           = "app-system-addons";
 const KEY_APP_SYSTEM_DEFAULTS         = "app-system-defaults";
 const KEY_APP_GLOBAL                  = "app-global";
@@ -1424,39 +1423,24 @@ this.XPIDatabase = {
                          encodeURIComponent(row.version));
     }
     fullCount += count;
 
     // The selected skin may come from an inactive theme (the default theme
     // when a lightweight theme is applied for example)
     text += "\r\n[ThemeDirs]\r\n";
 
-    let dssEnabled = Services.prefs.getBoolPref(PREF_EM_DSS_ENABLED, false);
-
-    let themes = [];
-    if (dssEnabled) {
-      themes = _filterDB(this.addonDB, aAddon => aAddon.type == "theme");
-    } else {
-      let activeTheme = _findAddon(
-        this.addonDB,
-        aAddon => (aAddon.type == "theme") &&
-                  (aAddon.internalName == XPIProvider.selectedSkin));
-      if (activeTheme) {
-        themes.push(activeTheme);
-      }
-    }
-
-    if (themes.length > 0) {
-      count = 0;
-      for (let row of themes) {
-        text += "Extension" + (count++) + "=" + row.descriptor + "\r\n";
-        enabledAddons.push(encodeURIComponent(row.id) + ":" +
-                           encodeURIComponent(row.version));
-      }
-      fullCount += count;
+    let dssEnabled = Services.prefs.getBoolPref(let activeTheme = _findAddon(
+      this.addonDB,
+      aAddon => (aAddon.type == "theme") &&
+                (aAddon.internalName == XPIProvider.selectedSkin));
+    if (activeTheme) {
+      text += "Extension" + (fullCount++) + "=" + activeTheme.descriptor + "\r\n";
+      enabledAddons.push(encodeURIComponent(activeTheme.id) + ":" +
+                         encodeURIComponent(activeTheme.version));
     }
 
     text += "\r\n[MultiprocessIncompatibleExtensions]\r\n";
 
     count = 0;
     for (let row of activeAddons) {
       if (!row.multiprocessCompatible) {
         text += "Extension" + (count++) + "=" + row.id + "\r\n";

deleted file mode 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_dss.js
+++ /dev/null
@@ -1,817 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
- * http://creativecommons.org/publicdomain/zero/1.0/
- */
-
-Components.utils.import("resource://gre/modules/NetUtil.jsm");
-
-// using a dynamic port in the addon metadata
-Components.utils.import("resource://testing-common/httpd.js");
-var gServer = new HttpServer();
-gServer.start(-1);
-gPort = gServer.identity.primaryPort;
-
-// This verifies that themes behave as expected
-
-const PREF_GENERAL_SKINS_SELECTEDSKIN = "general.skins.selectedSkin";
-const PREF_EXTENSIONS_DSS_ENABLED = "extensions.dss.enabled";
-
-Components.utils.import("resource://gre/modules/LightweightThemeManager.jsm");
-
-const profileDir = gProfD.clone();
-profileDir.append("extensions");
-
-// Observer to ensure a "lightweight-theme-styling-update" notification is sent
-// when expected
-var gLWThemeChanged = false;
-var LightweightThemeObserver = {
-  observe(aSubject, aTopic, aData) {
-    if (aTopic != "lightweight-theme-styling-update")
-      return;
-
-    gLWThemeChanged = true;
-  }
-};
-
-AM_Cc["@mozilla.org/observer-service;1"]
-     .getService(Components.interfaces.nsIObserverService)
-     .addObserver(LightweightThemeObserver, "lightweight-theme-styling-update", false);
-
-
-function run_test() {
-  do_test_pending();
-  createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "1.9.2");
-
-  Services.prefs.setCharPref(PREF_GENERAL_SKINS_SELECTEDSKIN, "theme1/1.0");
-  Services.prefs.setBoolPref(PREF_EXTENSIONS_DSS_ENABLED, true);
-  writeInstallRDFForExtension({
-    id: "theme1@tests.mozilla.org",
-    version: "1.0",
-    name: "Test 1",
-    type: 4,
-    internalName: "theme1/1.0",
-    targetApplications: [{
-      id: "xpcshell@tests.mozilla.org",
-      minVersion: "1",
-      maxVersion: "2"
-    }]
-  }, profileDir);
-
-  writeInstallRDFForExtension({
-    id: "theme2@tests.mozilla.org",
-    version: "1.0",
-    name: "Test 1",
-    internalName: "theme2/1.0",
-    targetApplications: [{
-      id: "xpcshell@tests.mozilla.org",
-      minVersion: "1",
-      maxVersion: "2"
-    }]
-  }, profileDir);
-
-  // We need a default theme for some of these things to work but we have hidden
-  // the one in the application directory.
-  writeInstallRDFForExtension({
-    id: "default@tests.mozilla.org",
-    version: "1.0",
-    name: "Default",
-    internalName: "classic/1.0",
-    targetApplications: [{
-      id: "xpcshell@tests.mozilla.org",
-      minVersion: "1",
-      maxVersion: "2"
-    }]
-  }, profileDir);
-
-  startupManager();
-  // Make sure we only register once despite multiple calls
-  AddonManager.addInstallListener(InstallListener);
-  AddonManager.addAddonListener(AddonListener);
-  AddonManager.addInstallListener(InstallListener);
-  AddonManager.addAddonListener(AddonListener);
-  AddonManager.addInstallListener(InstallListener);
-
-  AddonManager.getAddonsByIDs(["theme1@tests.mozilla.org",
-                               "theme2@tests.mozilla.org"], function([t1, t2]) {
-    do_check_neq(t1, null);
-    do_check_false(t1.userDisabled);
-    do_check_false(t1.appDisabled);
-    do_check_true(t1.isActive);
-    do_check_eq(t1.screenshots, null);
-    do_check_true(isThemeInAddonsList(profileDir, t1.id));
-    do_check_false(hasFlag(t1.permissions, AddonManager.PERM_CAN_DISABLE));
-    do_check_false(hasFlag(t1.permissions, AddonManager.PERM_CAN_ENABLE));
-
-    do_check_neq(t2, null);
-    do_check_true(t2.userDisabled);
-    do_check_false(t2.appDisabled);
-    do_check_false(t2.isActive);
-    do_check_eq(t2.screenshots, null);
-    do_check_true(isThemeInAddonsList(profileDir, t2.id));
-    do_check_false(hasFlag(t2.permissions, AddonManager.PERM_CAN_DISABLE));
-    do_check_true(hasFlag(t2.permissions, AddonManager.PERM_CAN_ENABLE));
-
-    do_execute_soon(run_test_1);
-  });
-}
-
-function end_test() {
-  do_execute_soon(do_test_finished);
-}
-
-// Checks enabling one theme disables the others
-function run_test_1() {
-  prepare_test({
-    "theme1@tests.mozilla.org": [
-      ["onDisabling", false],
-      "onDisabled"
-    ],
-    "theme2@tests.mozilla.org": [
-      ["onEnabling", false],
-      "onEnabled"
-    ]
-  });
-  AddonManager.getAddonsByIDs(["theme1@tests.mozilla.org",
-                               "theme2@tests.mozilla.org"], function([t1, t2]) {
-    t2.userDisabled = false;
-
-    ensure_test_completed();
-    do_check_false(hasFlag(t2.permissions, AddonManager.PERM_CAN_DISABLE));
-    do_check_false(hasFlag(t2.permissions, AddonManager.PERM_CAN_ENABLE));
-
-    do_check_true(t1.userDisabled);
-    do_check_false(hasFlag(t1.permissions, AddonManager.PERM_CAN_DISABLE));
-    do_check_true(hasFlag(t1.permissions, AddonManager.PERM_CAN_ENABLE));
-
-    do_execute_soon(check_test_1);
-  });
-}
-
-function check_test_1() {
-  restartManager();
-  do_check_eq(Services.prefs.getCharPref(PREF_GENERAL_SKINS_SELECTEDSKIN), "theme2/1.0");
-
-  AddonManager.getAddonsByIDs(["theme1@tests.mozilla.org",
-                               "theme2@tests.mozilla.org"], function([t1, t2]) {
-    do_check_neq(t1, null);
-    do_check_true(t1.userDisabled);
-    do_check_false(t1.appDisabled);
-    do_check_false(t1.isActive);
-    do_check_true(isThemeInAddonsList(profileDir, t1.id));
-    do_check_false(hasFlag(t1.permissions, AddonManager.PERM_CAN_DISABLE));
-    do_check_true(hasFlag(t1.permissions, AddonManager.PERM_CAN_ENABLE));
-
-    do_check_neq(t2, null);
-    do_check_false(t2.userDisabled);
-    do_check_false(t2.appDisabled);
-    do_check_true(t2.isActive);
-    do_check_true(isThemeInAddonsList(profileDir, t2.id));
-    do_check_false(hasFlag(t2.permissions, AddonManager.PERM_CAN_DISABLE));
-    do_check_false(hasFlag(t2.permissions, AddonManager.PERM_CAN_ENABLE));
-    do_check_false(gLWThemeChanged);
-
-    do_execute_soon(run_test_2);
-  });
-}
-
-// Removing the active theme should fall back to the default (not ideal in this
-// case since we don't have the default theme installed)
-function run_test_2() {
-  var dest = profileDir.clone();
-  dest.append(do_get_expected_addon_name("theme2@tests.mozilla.org"));
-  dest.remove(true);
-
-  restartManager();
-  do_check_eq(Services.prefs.getCharPref(PREF_GENERAL_SKINS_SELECTEDSKIN), "classic/1.0");
-
-  AddonManager.getAddonsByIDs(["theme1@tests.mozilla.org",
-                               "theme2@tests.mozilla.org"], function([t1, t2]) {
-    do_check_neq(t1, null);
-    do_check_true(t1.userDisabled);
-    do_check_false(t1.appDisabled);
-    do_check_false(t1.isActive);
-    do_check_true(isThemeInAddonsList(profileDir, t1.id));
-    do_check_false(hasFlag(t1.permissions, AddonManager.PERM_CAN_DISABLE));
-    do_check_true(hasFlag(t1.permissions, AddonManager.PERM_CAN_ENABLE));
-
-    do_check_eq(t2, null);
-    do_check_false(isThemeInAddonsList(profileDir, "theme2@tests.mozilla.org"));
-    do_check_false(gLWThemeChanged);
-
-    do_execute_soon(run_test_3);
-  });
-}
-
-// Installing a lightweight theme should happen instantly and disable the default theme
-function run_test_3() {
-  writeInstallRDFForExtension({
-    id: "theme2@tests.mozilla.org",
-    version: "1.0",
-    name: "Test 1",
-    internalName: "theme2/1.0",
-    targetApplications: [{
-      id: "xpcshell@tests.mozilla.org",
-      minVersion: "1",
-      maxVersion: "2"
-    }]
-  }, profileDir);
-  restartManager();
-
-  prepare_test({
-    "1@personas.mozilla.org": [
-      ["onInstalling", false],
-      "onInstalled",
-      ["onEnabling", false],
-      "onEnabled"
-    ],
-    "default@tests.mozilla.org": [
-      ["onDisabling", false],
-      "onDisabled",
-    ]
-  }, [
-    "onExternalInstall"
-  ]);
-
-  LightweightThemeManager.currentTheme = {
-    id: "1",
-    version: "1",
-    name: "Test LW Theme",
-    description: "A test theme",
-    author: "Mozilla",
-    homepageURL: "http://localhost:" + gPort + "/data/index.html",
-    headerURL: "http://localhost:" + gPort + "/data/header.png",
-    footerURL: "http://localhost:" + gPort + "/data/footer.png",
-    previewURL: "http://localhost:" + gPort + "/data/preview.png",
-    iconURL: "http://localhost:" + gPort + "/data/icon.png"
-  };
-
-  ensure_test_completed();
-
-  AddonManager.getAddonByID("1@personas.mozilla.org", function(p1) {
-    do_check_neq(null, p1);
-    do_check_eq(p1.name, "Test LW Theme");
-    do_check_eq(p1.version, "1");
-    do_check_eq(p1.type, "theme");
-    do_check_eq(p1.description, "A test theme");
-    do_check_eq(p1.creator, "Mozilla");
-    do_check_eq(p1.homepageURL, "http://localhost:" + gPort + "/data/index.html");
-    do_check_eq(p1.iconURL, "http://localhost:" + gPort + "/data/icon.png");
-    do_check_eq(p1.screenshots.length, 1);
-    do_check_eq(p1.screenshots[0], "http://localhost:" + gPort + "/data/preview.png");
-    do_check_false(p1.appDisabled);
-    do_check_false(p1.userDisabled);
-    do_check_true(p1.isCompatible);
-    do_check_true(p1.providesUpdatesSecurely);
-    do_check_eq(p1.blocklistState, 0);
-    do_check_true(p1.isActive);
-    do_check_eq(p1.pendingOperations, 0);
-    do_check_eq(p1.permissions, AddonManager.PERM_CAN_UNINSTALL | AddonManager.PERM_CAN_DISABLE);
-    do_check_eq(p1.scope, AddonManager.SCOPE_PROFILE);
-    do_check_true("isCompatibleWith" in p1);
-    do_check_true("findUpdates" in p1);
-
-    AddonManager.getAddonsByTypes(["theme"], function(addons) {
-      let seen = false;
-      addons.forEach(function(a) {
-        if (a.id == "1@personas.mozilla.org") {
-          seen = true;
-        } else {
-          dump("Checking theme " + a.id + "\n");
-          do_check_false(a.isActive);
-          do_check_true(a.userDisabled);
-        }
-      });
-      do_check_true(seen);
-
-      do_check_true(gLWThemeChanged);
-      gLWThemeChanged = false;
-
-      do_execute_soon(run_test_4);
-    });
-  });
-}
-
-// Installing a second lightweight theme should disable the first with no restart
-function run_test_4() {
-  prepare_test({
-    "1@personas.mozilla.org": [
-      ["onDisabling", false],
-      "onDisabled",
-    ],
-    "2@personas.mozilla.org": [
-      ["onInstalling", false],
-      "onInstalled",
-      ["onEnabling", false],
-      "onEnabled"
-    ]
-  }, [
-    "onExternalInstall"
-  ]);
-
-  LightweightThemeManager.currentTheme = {
-    id: "2",
-    version: "1",
-    name: "Test LW Theme",
-    description: "A second test theme",
-    author: "Mozilla",
-    homepageURL: "http://localhost:" + gPort + "/data/index.html",
-    headerURL: "http://localhost:" + gPort + "/data/header.png",
-    footerURL: "http://localhost:" + gPort + "/data/footer.png",
-    previewURL: "http://localhost:" + gPort + "/data/preview.png",
-    iconURL: "http://localhost:" + gPort + "/data/icon.png"
-  };
-
-  ensure_test_completed();
-
-  AddonManager.getAddonsByIDs(["1@personas.mozilla.org",
-                               "2@personas.mozilla.org"], function([p1, p2]) {
-    do_check_neq(null, p2);
-    do_check_false(p2.appDisabled);
-    do_check_false(p2.userDisabled);
-    do_check_true(p2.isActive);
-    do_check_eq(p2.pendingOperations, 0);
-    do_check_eq(p2.permissions, AddonManager.PERM_CAN_UNINSTALL | AddonManager.PERM_CAN_DISABLE);
-
-    do_check_neq(null, p1);
-    do_check_false(p1.appDisabled);
-    do_check_true(p1.userDisabled);
-    do_check_false(p1.isActive);
-    do_check_eq(p1.pendingOperations, 0);
-    do_check_eq(p1.permissions, AddonManager.PERM_CAN_UNINSTALL | AddonManager.PERM_CAN_ENABLE);
-
-    AddonManager.getAddonsByTypes(["theme"], function(addons) {
-      let seen = false;
-      addons.forEach(function(a) {
-        if (a.id == "2@personas.mozilla.org") {
-          seen = true;
-        } else {
-          dump("Checking theme " + a.id + "\n");
-          do_check_false(a.isActive);
-          do_check_true(a.userDisabled);
-        }
-      });
-      do_check_true(seen);
-
-      do_check_true(gLWThemeChanged);
-      gLWThemeChanged = false;
-
-      do_execute_soon(run_test_5);
-    });
-  });
-}
-
-// Switching to a custom theme should disable the lightweight theme and require
-// a restart. Cancelling that should also be possible.
-function run_test_5() {
-  prepare_test({
-    "2@personas.mozilla.org": [
-      ["onDisabling", false],
-      "onDisabled"
-    ],
-    "theme2@tests.mozilla.org": [
-      ["onEnabling", false],
-      "onEnabled"
-    ]
-  });
-
-  AddonManager.getAddonsByIDs(["2@personas.mozilla.org",
-                               "theme2@tests.mozilla.org"], function([p2, t2]) {
-    t2.userDisabled = false;
-
-    ensure_test_completed();
-
-    prepare_test({
-      "2@personas.mozilla.org": [
-        "onEnabling"
-      ],
-      "theme2@tests.mozilla.org": [
-        "onDisabling"
-      ]
-    });
-
-    p2.userDisabled = false;
-
-    ensure_test_completed();
-
-    prepare_test({
-      "2@personas.mozilla.org": [
-        "onOperationCancelled"
-      ],
-      "theme2@tests.mozilla.org": [
-        "onOperationCancelled"
-      ]
-    });
-
-    t2.userDisabled = false;
-
-    ensure_test_completed();
-
-    do_check_true(t2.isActive);
-    do_check_false(t2.userDisabled);
-    do_check_false(hasFlag(AddonManager.PENDING_ENABLE, t2.pendingOperations));
-    do_check_false(p2.isActive);
-    do_check_true(p2.userDisabled);
-    do_check_false(hasFlag(AddonManager.PENDING_DISABLE, p2.pendingOperations));
-    do_check_true(hasFlag(AddonManager.PERM_CAN_ENABLE, p2.permissions));
-    do_check_true(gLWThemeChanged);
-
-    do_execute_soon(check_test_5);
-  });
-}
-
-function check_test_5() {
-  restartManager();
-
-  AddonManager.getAddonsByIDs(["2@personas.mozilla.org",
-                               "theme2@tests.mozilla.org"], function([p2, t2]) {
-    do_check_true(t2.isActive);
-    do_check_false(t2.userDisabled);
-    do_check_false(hasFlag(AddonManager.PENDING_ENABLE, t2.pendingOperations));
-    do_check_false(p2.isActive);
-    do_check_true(p2.userDisabled);
-    do_check_false(hasFlag(AddonManager.PENDING_DISABLE, p2.pendingOperations));
-
-    do_check_true(gLWThemeChanged);
-    gLWThemeChanged = false;
-
-    do_execute_soon(run_test_6);
-  });
-}
-
-// Switching from a custom theme to a lightweight theme should require a restart
-function run_test_6() {
-  prepare_test({
-    "2@personas.mozilla.org": [
-      "onEnabling",
-    ],
-    "theme2@tests.mozilla.org": [
-      "onDisabling"
-    ]
-  });
-
-  AddonManager.getAddonsByIDs(["2@personas.mozilla.org",
-                               "theme2@tests.mozilla.org"], function([p2, t2]) {
-    p2.userDisabled = false;
-
-    ensure_test_completed();
-
-    prepare_test({
-      "2@personas.mozilla.org": [
-        "onOperationCancelled",
-      ],
-      "theme2@tests.mozilla.org": [
-        "onOperationCancelled"
-      ]
-    });
-
-    t2.userDisabled = false;
-
-    ensure_test_completed();
-
-    prepare_test({
-      "2@personas.mozilla.org": [
-        "onEnabling",
-      ],
-      "theme2@tests.mozilla.org": [
-        "onDisabling"
-      ]
-    });
-
-    p2.userDisabled = false;
-
-    ensure_test_completed();
-
-    do_check_false(p2.isActive);
-    do_check_false(p2.userDisabled);
-    do_check_true(hasFlag(AddonManager.PENDING_ENABLE, p2.pendingOperations));
-    do_check_true(t2.isActive);
-    do_check_true(t2.userDisabled);
-    do_check_true(hasFlag(AddonManager.PENDING_DISABLE, t2.pendingOperations));
-    do_check_false(gLWThemeChanged);
-
-    do_execute_soon(check_test_6);
-  });
-}
-
-function check_test_6() {
-  restartManager();
-
-  AddonManager.getAddonsByIDs(["2@personas.mozilla.org",
-                               "theme2@tests.mozilla.org"], function([p2, t2]) {
-    do_check_true(p2.isActive);
-    do_check_false(p2.userDisabled);
-    do_check_false(hasFlag(AddonManager.PENDING_ENABLE, p2.pendingOperations));
-    do_check_false(t2.isActive);
-    do_check_true(t2.userDisabled);
-    do_check_false(hasFlag(AddonManager.PENDING_DISABLE, t2.pendingOperations));
-
-    do_check_true(gLWThemeChanged);
-    gLWThemeChanged = false;
-
-    do_execute_soon(run_test_7);
-  });
-}
-
-// Uninstalling a lightweight theme should not require a restart
-function run_test_7() {
-  prepare_test({
-    "1@personas.mozilla.org": [
-      ["onUninstalling", false],
-      "onUninstalled"
-    ]
-  });
-
-  AddonManager.getAddonByID("1@personas.mozilla.org", function(p1) {
-    p1.uninstall();
-
-    ensure_test_completed();
-    do_check_eq(LightweightThemeManager.usedThemes.length, 1);
-    do_check_false(gLWThemeChanged);
-
-    do_execute_soon(run_test_8);
-  });
-}
-
-// Uninstalling a lightweight theme in use should not require a restart and it
-// should reactivate the default theme
-// Also, uninstalling a lightweight theme in use should send a
-// "lightweight-theme-styling-update" notification through the observer service
-function run_test_8() {
-  prepare_test({
-    "2@personas.mozilla.org": [
-      ["onUninstalling", false],
-      "onUninstalled"
-    ],
-    "default@tests.mozilla.org": [
-      ["onEnabling", false],
-      "onEnabled"
-    ]
-  });
-
-  AddonManager.getAddonByID("2@personas.mozilla.org", function(p2) {
-    p2.uninstall();
-
-    ensure_test_completed();
-    do_check_eq(LightweightThemeManager.usedThemes.length, 0);
-
-    do_check_true(gLWThemeChanged);
-    gLWThemeChanged = false;
-
-    do_execute_soon(run_test_9);
-  });
-}
-
-// Uninstalling a theme not in use should not require a restart
-function run_test_9() {
-  AddonManager.getAddonByID("theme1@tests.mozilla.org", function(t1) {
-    prepare_test({
-      "theme1@tests.mozilla.org": [
-        ["onUninstalling", false],
-        "onUninstalled"
-      ]
-    });
-
-    t1.uninstall();
-
-    ensure_test_completed();
-
-    AddonManager.getAddonByID("theme1@tests.mozilla.org", function(newt1) {
-      do_check_eq(newt1, null);
-      do_check_false(gLWThemeChanged);
-
-      do_execute_soon(run_test_10);
-    });
-  });
-}
-
-// Uninstalling a custom theme in use should require a restart
-function run_test_10() {
-  AddonManager.getAddonByID("theme2@tests.mozilla.org", callback_soon(function(oldt2) {
-    prepare_test({
-      "theme2@tests.mozilla.org": [
-        ["onEnabling", false],
-        "onEnabled"
-      ],
-      "default@tests.mozilla.org": [
-        ["onDisabling", false],
-        "onDisabled"
-      ]
-    });
-
-    oldt2.userDisabled = false;
-
-    ensure_test_completed();
-
-    restartManager();
-
-    AddonManager.getAddonsByIDs(["default@tests.mozilla.org",
-                                 "theme2@tests.mozilla.org"],
-                                 callback_soon(function([d, t2]) {
-      do_check_true(t2.isActive);
-      do_check_false(t2.userDisabled);
-      do_check_false(t2.appDisabled);
-      do_check_false(d.isActive);
-      do_check_true(d.userDisabled);
-      do_check_false(d.appDisabled);
-
-      prepare_test({
-        "theme2@tests.mozilla.org": [
-          ["onUninstalling", false],
-          "onUninstalled"
-        ],
-        "default@tests.mozilla.org": [
-          ["onEnabling", false],
-          "onEnabled"
-        ]
-      });
-
-      t2.uninstall();
-
-      ensure_test_completed();
-      do_check_false(gLWThemeChanged);
-
-      restartManager();
-
-      do_execute_soon(run_test_11);
-    }));
-  }));
-}
-
-// Installing a custom theme not in use should not require a restart
-function run_test_11() {
-  prepare_test({ }, [
-    "onNewInstall"
-  ]);
-
-  AddonManager.getInstallForFile(do_get_addon("test_theme"), function(install) {
-    ensure_test_completed();
-
-    do_check_neq(install, null);
-    do_check_eq(install.type, "theme");
-    do_check_eq(install.version, "1.0");
-    do_check_eq(install.name, "Test Theme 1");
-    do_check_eq(install.state, AddonManager.STATE_DOWNLOADED);
-
-    prepare_test({
-      "theme1@tests.mozilla.org": [
-        ["onInstalling", false],
-        "onInstalled"
-      ]
-    }, [
-      "onInstallStarted",
-      "onInstallEnded",
-    ], callback_soon(check_test_11));
-    install.install();
-  });
-}
-
-function check_test_11() {
-  restartManager();
-  AddonManager.getAddonByID("theme1@tests.mozilla.org", function(t1) {
-    do_check_neq(t1, null);
-    var previewSpec = do_get_addon_root_uri(profileDir, "theme1@tests.mozilla.org") + "preview.png";
-    do_check_eq(t1.screenshots.length, 1);
-    do_check_eq(t1.screenshots[0], previewSpec);
-    do_check_false(gLWThemeChanged);
-
-    do_execute_soon(run_test_12);
-  });
-}
-
-// Updating a custom theme not in use should not require a restart
-function run_test_12() {
-  prepare_test({ }, [
-    "onNewInstall"
-  ]);
-
-  AddonManager.getInstallForFile(do_get_addon("test_theme"), function(install) {
-    ensure_test_completed();
-
-    do_check_neq(install, null);
-    do_check_eq(install.type, "theme");
-    do_check_eq(install.version, "1.0");
-    do_check_eq(install.name, "Test Theme 1");
-    do_check_eq(install.state, AddonManager.STATE_DOWNLOADED);
-
-    prepare_test({
-      "theme1@tests.mozilla.org": [
-        ["onInstalling", false],
-        "onInstalled"
-      ]
-    }, [
-      "onInstallStarted",
-      "onInstallEnded",
-    ], check_test_12);
-    install.install();
-  });
-}
-
-function check_test_12() {
-  AddonManager.getAddonByID("theme1@tests.mozilla.org", function(t1) {
-    do_check_neq(t1, null);
-    do_check_false(gLWThemeChanged);
-
-    do_execute_soon(run_test_13);
-  });
-}
-
-// Updating a custom theme in use should require a restart
-function run_test_13() {
-  AddonManager.getAddonByID("theme1@tests.mozilla.org", callback_soon(function(t1) {
-    prepare_test({
-      "theme1@tests.mozilla.org": [
-        ["onEnabling", false],
-        "onEnabled"
-      ],
-      "default@tests.mozilla.org": [
-        ["onDisabling", false],
-        "onDisabled"
-      ]
-    });
-
-    t1.userDisabled = false;
-    ensure_test_completed();
-    restartManager();
-
-    prepare_test({ }, [
-      "onNewInstall"
-    ]);
-
-    AddonManager.getInstallForFile(do_get_addon("test_theme"), function(install) {
-      ensure_test_completed();
-
-      do_check_neq(install, null);
-      do_check_eq(install.type, "theme");
-      do_check_eq(install.version, "1.0");
-      do_check_eq(install.name, "Test Theme 1");
-      do_check_eq(install.state, AddonManager.STATE_DOWNLOADED);
-
-      prepare_test({
-        "theme1@tests.mozilla.org": [
-          "onInstalling",
-        ]
-      }, [
-        "onInstallStarted",
-        "onInstallEnded",
-      ], callback_soon(check_test_13));
-      install.install();
-    });
-  }));
-}
-
-function check_test_13() {
-  restartManager();
-
-  AddonManager.getAddonByID("theme1@tests.mozilla.org", function(t1) {
-    do_check_neq(t1, null);
-    do_check_true(t1.isActive);
-    do_check_false(gLWThemeChanged);
-    t1.uninstall();
-
-    do_execute_soon(run_test_14);
-  });
-}
-
-// Switching from a lightweight theme to the default theme should not require
-// a restart
-function run_test_14() {
-  restartManager();
-  LightweightThemeManager.currentTheme = {
-    id: "1",
-    version: "1",
-    name: "Test LW Theme",
-    description: "A test theme",
-    author: "Mozilla",
-    homepageURL: "http://localhost:" + gPort + "/data/index.html",
-    headerURL: "http://localhost:" + gPort + "/data/header.png",
-    footerURL: "http://localhost:" + gPort + "/data/footer.png",
-    previewURL: "http://localhost:" + gPort + "/data/preview.png",
-    iconURL: "http://localhost:" + gPort + "/data/icon.png"
-  };
-
-  AddonManager.getAddonByID("default@tests.mozilla.org", function(d) {
-    do_check_true(d.userDisabled);
-    do_check_false(d.isActive);
-
-    prepare_test({
-      "1@personas.mozilla.org": [
-        ["onDisabling", false],
-        "onDisabled"
-      ],
-      "default@tests.mozilla.org": [
-        ["onEnabling", false],
-        "onEnabled"
-      ]
-    });
-
-    d.userDisabled = false;
-    ensure_test_completed();
-
-    do_check_false(d.userDisabled);
-    do_check_true(d.isActive);
-
-    do_check_true(gLWThemeChanged);
-    gLWThemeChanged = false;
-
-    end_test();
-  });
-}

--- a/toolkit/mozapps/extensions/test/xpcshell/test_webextension_theme.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_webextension_theme.js
@@ -168,17 +168,17 @@ function* setDisabledStateAndCheck(which
       "There should be no pending operations left");
     if (!isDisabled)
       gActiveTheme = theme.id;
   }
 
   ensure_test_completed();
 }
 
-add_task(function* test_dss_themes() {
+add_task(function* test_complete_themes() {
   // Enable the complete theme.
   yield* setDisabledStateAndCheck(THEME_IDS[0]);
 
   // Disabling the complete theme should revert to the default theme.
   yield* setDisabledStateAndCheck(THEME_IDS[0], true);
 
   // Enable it again.
   yield* setDisabledStateAndCheck(THEME_IDS[0]);

--- a/toolkit/mozapps/extensions/test/xpcshell/xpcshell-shared.ini
+++ b/toolkit/mozapps/extensions/test/xpcshell/xpcshell-shared.ini
@@ -178,19 +178,16 @@ tags = blocklist
 [test_corrupt_strictcompat.js]
 [test_corruptfile.js]
 [test_dataDirectory.js]
 [test_default_providers_pref.js]
 [test_dictionary.js]
 [test_langpack.js]
 [test_disable.js]
 [test_distribution.js]
-[test_dss.js]
-# Bug 676992: test consistently fails on Android
-fail-if = os == "android"
 [test_duplicateplugins.js]
 # Bug 676992: test consistently hangs on Android
 skip-if = os == "android"
 [test_error.js]
 [test_experiment.js]
 [test_filepointer.js]
 # Bug 676992: test consistently hangs on Android
 skip-if = os == "android"