diff -r 000000000000 -r 6474c204b198 testing/mochitest/mochitest-e10s-utils.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/testing/mochitest/mochitest-e10s-utils.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,87 @@
+// Utilities for running tests in an e10s environment.
+
+// There are some tricks/shortcuts that test code takes that we don't see
+// in the real browser code.  These include setting content.location.href
+// (which doesn't work in test code with e10s enabled as the document object
+// is yet to be created), waiting for certain events the main browser doesn't
+// care about and so doesn't normally get special support, eg, the "pageshow"
+// or "load" events).
+// So we make some hacks to pretend these work in the test suite.
+
+// Ideally all these hacks could be removed, but this can only happen when
+// the tests are refactored to not use these tricks.  But this would be a huge
+// amount of work and is unlikely to happen anytime soon...
+
+const CONTENT_URL = "chrome://mochikit/content/mochitest-e10s-utils-content.js";
+
+// This is an object that is used as the "location" on a remote document or
+// window.  It will be overwritten as the real document and window are made
+// available.
+let locationStub = function(browser) {
+  this.browser = browser;
+};
+locationStub.prototype = {
+  get href() {
+    return this.browser.webNavigation.currentURI.spec;
+  },
+  set href(val) {
+    this.browser.loadURI(val);
+  },
+  assign: function(url) {
+    this.href = url;
+  }
+};
+
+// This object is used in place of contentWindow while we wait for it to be
+// overwritten as the real window becomes available.
+let TemporaryWindowStub = function(browser) {
+  this._locationStub = new locationStub(browser);
+};
+
+TemporaryWindowStub.prototype = {
+  // save poor developers from getting confused about why the window isn't
+  // working like a window should..
+  toString: function() {
+    return "[Window Stub for e10s tests]";
+  },
+  get location() {
+    return this._locationStub;
+  },
+  set location(val) {
+    this._locationStub.href = val;
+  },
+  get document() {
+    // so tests can say: document.location....
+    return this;
+  }
+};
+
+// An observer called when a new remote browser element is created.  We replace
+// the _contentWindow in new browsers with our TemporaryWindowStub object.
+function observeNewFrameloader(subject, topic, data) {
+  let browser = subject.QueryInterface(Ci.nsIFrameLoader).ownerElement;
+  browser._contentWindow = new TemporaryWindowStub(browser);
+}
+
+function e10s_init() {
+  // Use the global message manager to inject a content script into all browsers.
+  let globalMM = Cc["@mozilla.org/globalmessagemanager;1"]
+                   .getService(Ci.nsIMessageListenerManager);
+  globalMM.loadFrameScript(CONTENT_URL, true);
+  globalMM.addMessageListener("Test:Event", function(message) {
+    let event = document.createEvent('HTMLEvents');
+    event.initEvent(message.data.name, true, true, {});
+    message.target.dispatchEvent(event);
+  });
+
+  // We add an observer so we can notice new <browser> elements created
+  Services.obs.addObserver(observeNewFrameloader, "remote-browser-shown", false);
+
+  // Listen for an 'oop-browser-crashed' event and log it so people analysing
+  // test logs have a clue about what is going on.
+  window.addEventListener("oop-browser-crashed", (event) => {
+    let uri = event.target.currentURI;
+    Cu.reportError("remote browser crashed while on " +
+                   (uri ? uri.spec : "<unknown>") + "\n");
+  }, true);
+}