--- a/docshell/test/browser/browser.ini
+++ b/docshell/test/browser/browser.ini
@@ -129,19 +129,19 @@ skip-if = true # Bug 1220415
 [browser_timelineMarkers-03.js]
 [browser_timelineMarkers-04.js]
 [browser_timelineMarkers-05.js]
 [browser_ua_emulation.js]
 [browser_history_triggeringprincipal_viewsource.js]
 [browser_click_link_within_view_source.js]
 [browser_browsingContext-01.js]
 [browser_browsingContext-02.js]
-fail-if = fission
+skip-if = fission # Cross-process postMessage
 [browser_browsingContext-03.js]
-fail-if = fission
+skip-if = fission # Cross-process postMessage
 [browser_browsingContext-embedder.js]
 [browser_csp_uir.js]
 support-files =
   file_csp_uir.html
   file_csp_uir_dummy.html
 [browser_cross_process_csp_inheritance.js]
 fail-if = fission
 skip-if = !e10s # e10s specific test.

--- a/docshell/test/browser/browser_browsingContext-02.js
+++ b/docshell/test/browser/browser_browsingContext-02.js
@@ -27,54 +27,66 @@ add_task(async function() {
         URL + "#seventh",
         true,
         true
       );
       await ContentTask.spawn(
         browser,
         { base1: BASE1, base2: BASE2 },
         async function({ base1, base2 }) {
-          let top = content.window;
+          let top = content;
           top.name = "top";
           top.location.href += "#top";
 
           let contexts = {
             top: top.location.href,
             first: base1 + "dummy_page.html#first",
             third: base2 + "dummy_page.html#third",
             second: base1 + "dummy_page.html#second",
             fourth: base2 + "dummy_page.html#fourth",
             fifth: base1 + "dummy_page.html#fifth",
             sixth: base1 + "onload_message.html#sixth",
             seventh: base1 + "onload_message.html#seventh",
           };
 
           function addFrame(target, name) {
-            let doc = (target.contentWindow || target).document;
-            let frame = doc.createElement("iframe");
-            let p = new Promise(
-              resolve => (frame.onload = () => resolve(frame))
+            return content.SpecialPowers.spawn(
+              target,
+              [name, contexts[name]],
+              async (name, context) => {
+                let doc = this.content.document;
+
+                let frame = doc.createElement("iframe");
+                doc.body.appendChild(frame);
+                frame.name = name;
+                frame.src = context;
+                await new Promise(resolve => {
+                  frame.addEventListener("load", resolve, { once: true });
+                });
+                return frame.browsingContext;
+              }
             );
-            doc.body.appendChild(frame);
-            frame.name = name;
-            frame.src = contexts[name];
-            return p;
           }
 
           function addWindow(target, name, { options, resolve }) {
-            var win = target.contentWindow.open(contexts[name], name, options);
+            return content.SpecialPowers.spawn(
+              target,
+              [name, contexts[name], options, resolve],
+              (name, context, options, resolve) => {
+                let win = this.content.open(context, name, options);
+                let bc = win && win.docShell.browsingContext;
 
-            if (resolve) {
-              return new Promise(resolve =>
-                target.contentWindow.addEventListener("message", () =>
-                  resolve(win)
-                )
-              );
-            }
-            return Promise.resolve({ name });
+                if (resolve) {
+                  return new Promise(resolve =>
+                    this.content.addEventListener("message", () => resolve(bc))
+                  );
+                }
+                return Promise.resolve({ name });
+              }
+            );
           }
 
           // We're going to create a tree that looks like the
           // following.
           //
           //           top          sixth    seventh
           //          /   \
           //         /     \        /
@@ -88,35 +100,31 @@ add_task(async function() {
           //
           // The idea is to have one top level non-auxiliary browsing
           // context, five nested, one top level auxiliary with an
           // opener, and one top level without an opener. Given that
           // set of related and one unrelated browsing contexts we
           // wish to confirm that targeting is able to find
           // appropriate browsing contexts.
 
-          function bc(frame) {
-            return (frame.contentWindow || frame).docShell.browsingContext;
-          }
-
           function reachable(start, targets) {
             for (let target of targets) {
               is(
-                bc(start).findWithName(target.name, bc(start)),
-                bc(target),
-                [bc(start).name, "can reach", target.name].join(" ")
+                start.findWithName(target.name, start),
+                target,
+                [start.name, "can reach", target.name].join(" ")
               );
             }
           }
 
           function unreachable(start, target) {
             is(
-              bc(start).findWithName(target.name, bc(start)),
+              start.findWithName(target.name, start),
               null,
-              [bc(start).name, "can't reach", target.name].join(" ")
+              [start.name, "can't reach", target.name].join(" ")
             );
           }
 
           let first = await addFrame(top, "first");
           info("first");
           let second = await addFrame(top, "second");
           info("second");
           let third = await addFrame(first, "third");
@@ -127,17 +135,25 @@ add_task(async function() {
           info("fifth");
           let sixth = await addWindow(fourth, "sixth", { resolve: true });
           info("sixth");
           let seventh = await addWindow(fourth, "seventh", {
             options: ["noopener"],
           });
           info("seventh");
 
-          let frames = [top, first, second, third, fourth, fifth, sixth];
+          let frames = [
+            BrowsingContext.getFromWindow(top),
+            first,
+            second,
+            third,
+            fourth,
+            fifth,
+            sixth,
+          ];
           for (let start of frames) {
             reachable(start, frames);
             unreachable(start, seventh);
           }
         }
       );
 
       for (let tab of await Promise.all([sixth, seventh])) {

--- a/docshell/test/browser/browser_browsingContext-03.js
+++ b/docshell/test/browser/browser_browsingContext-03.js
@@ -21,49 +21,61 @@ add_task(async function() {
         URL + "#sixth",
         true,
         true
       );
       await ContentTask.spawn(
         browser,
         { base1: BASE1, base2: BASE2 },
         async function({ base1, base2 }) {
-          let top = content.window;
+          let top = content;
           top.name = "top";
           top.location.href += "#top";
 
           let contexts = {
             top: top.location.href,
             first: base1 + "dummy_page.html#first",
             third: base2 + "dummy_page.html#third",
             second: base1 + "dummy_page.html#second",
             fourth: base2 + "dummy_page.html#fourth",
             fifth: base1 + "dummy_page.html#fifth",
             sixth: base1 + "onload_message.html#sixth",
           };
 
           function addFrame(target, name) {
-            let doc = (target.contentWindow || target).document;
-            let frame = doc.createElement("iframe");
-            let p = new Promise(
-              resolve => (frame.onload = () => resolve(frame))
+            return content.SpecialPowers.spawn(
+              target,
+              [name, contexts[name]],
+              async (name, context) => {
+                let doc = this.content.document;
+
+                let frame = doc.createElement("iframe");
+                doc.body.appendChild(frame);
+                frame.name = name;
+                frame.src = context;
+                await new Promise(resolve => {
+                  frame.addEventListener("load", resolve, { once: true });
+                });
+                return frame.browsingContext;
+              }
             );
-            doc.body.appendChild(frame);
-            frame.name = name;
-            frame.src = contexts[name];
-            return p;
           }
 
           function addWindow(target, name) {
-            var win = target.contentWindow.open(contexts[name], name);
+            return content.SpecialPowers.spawn(
+              target,
+              [name, contexts[name]],
+              (name, context) => {
+                let win = this.content.open(context, name);
+                let bc = win && win.docShell.browsingContext;
 
-            return new Promise(resolve =>
-              target.contentWindow.addEventListener("message", () =>
-                resolve(win)
-              )
+                return new Promise(resolve =>
+                  this.content.addEventListener("message", () => resolve(bc))
+                );
+              }
             );
           }
 
           // Generate all lists of length length with every combination of
           // values in input
           function* generate(input, length) {
             let list = new Array(length);
 
@@ -98,29 +110,32 @@ add_task(async function() {
           // context, five nested, one top level auxiliary with an
           // opener. Given that set of related browsing contexts we
           // wish to confirm that targeting is semantically equivalent
           // with how nsIDocShellTreeItem.findItemWithName works. The
           // trick to ensure that is to give all frames the same name!
           // and ensure that the find algorithms return the same nodes
           // in the same order.
 
-          function bc(frame) {
-            return (frame.contentWindow || frame).docShell.browsingContext;
-          }
-
           let first = await addFrame(top, "first");
           let second = await addFrame(top, "second");
           let third = await addFrame(first, "third");
           let fourth = await addFrame(first, "fourth");
           let fifth = await addFrame(fourth, "fifth");
           let sixth = await addWindow(fourth, "sixth");
 
-          let frames = [top, first, second, third, fourth, fifth, sixth];
-          let browsingContexts = frames.map(bc);
+          let browsingContexts = [
+            BrowsingContext.getFromWindow(top),
+            first,
+            second,
+            third,
+            fourth,
+            fifth,
+            sixth,
+          ];
           let docShells = browsingContexts.map(context => context.docShell);
 
           ok(
             top.docShell instanceof Ci.nsIDocShellTreeItem,
             "When we remove nsIDocShellTreeItem this test should be removed"
           );
 
           // For every browsing context we generate all possible

--- a/testing/specialpowers/content/SpecialPowersChild.jsm
+++ b/testing/specialpowers/content/SpecialPowersChild.jsm
@@ -50,16 +50,17 @@ class SpecialPowersChild extends Special
   }
 
   attachToWindow() {
     let window = this.contentWindow;
     if (!window.wrappedJSObject.SpecialPowers) {
       this._windowID = window.windowUtils.currentInnerWindowID;
       this.DOMWindowUtils = bindDOMWindowUtils(window);
 
+      window.SpecialPowers = this;
       window.wrappedJSObject.SpecialPowers = this;
       if (this.IsInNestedFrame) {
         this.addPermission("allowXULXBL", true, window.document);
       }
     }
   }
 
   get window() {