diff -r 000000000000 -r 6474c204b198 dom/browser-element/mochitest/browserElement_OpenMixedProcess.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/browser-element/mochitest/browserElement_OpenMixedProcess.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,106 @@
+/* Any copyright is dedicated to the public domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Bug 776129 - If a window w calls window.open, the resultant window should be
+// remote iff w is remote.
+//
+// <iframe mozbrowser> can be default-OOP or default-in-process.  But we can
+// override this default by setting remote=true or remote=false on the iframe.
+//
+// This bug arises when we are default-in-process and a OOP iframe calls
+// window.open, or when we're default-OOP and an in-process iframe calls
+// window.open.  In either case, if the opened iframe gets the default
+// remotness, it will not match its opener's remoteness, which is bad.
+//
+// Since the name of the test determines the OOP-by-default pref, the "inproc"
+// version of this test opens an OOP frame, and the "oop" version opens an
+// in-process frame.  Enjoy.  :)
+
+"use strict";
+
+SimpleTest.waitForExplicitFinish();
+browserElementTestHelpers.setEnabledPref(true);
+browserElementTestHelpers.addPermission();
+
+function runTest() {
+  // We're going to open a remote frame if OOP off by default.  If OOP is on by
+  // default, we're going to open an in-process frame.
+  var remote = !browserElementTestHelpers.getOOPByDefaultPref();
+
+  var iframe = document.createElement('iframe');
+  SpecialPowers.wrap(iframe).mozbrowser = true;
+  iframe.setAttribute('remote', remote);
+
+  // The page we load does window.open, then checks some things and reports
+  // back using alert().  Finally, it calls alert('finish').
+  //
+  // Bug 776129 in particular manifests itself such that the popup frame loads
+  // and the tests in file_browserElement_OpenMixedProcess pass, but the
+  // content of the frame is invisible.  To catch this case, we take a
+  // screenshot after we load the content into the popup, and ensure that it's
+  // not blank.
+  var popup;
+  iframe.addEventListener('mozbrowseropenwindow', function(e) {
+    popup = document.body.appendChild(e.detail.frameElement);
+  });
+
+  iframe.addEventListener('mozbrowsershowmodalprompt', function(e) {
+    if (e.detail.message.startsWith('pass')) {
+      ok(true, e.detail.message);
+    }
+    else if (e.detail.message.startsWith('fail')) {
+      ok(false, e.detail.message);
+    }
+    else if (e.detail.message == 'finish') {
+      // We assume here that iframe is completely blank, and spin until popup's
+      // screenshot is not the same as iframe.
+      iframe.getScreenshot(1000, 1000).onsuccess = function(e) {
+        var fr = new FileReader();
+        fr.onloadend = function() { test2(popup, fr.result); };
+        fr.readAsArrayBuffer(e.target.result);
+      };
+    }
+    else {
+      ok(false, e.detail.message, "Unexpected message!");
+    }
+  });
+
+  document.body.appendChild(iframe);
+  iframe.src = 'file_browserElement_OpenMixedProcess.html';
+}
+
+function arrayBuffersEqual(a, b) {
+  var x = new Int8Array(a);
+  var y = new Int8Array(b);
+  if (x.length != y.length) {
+    return false;
+  }
+
+  for (var i = 0; i < x.length; i++) {
+    if (x[i] != y[i]) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+function test2(popup, blankScreenshotArrayBuffer) {
+  // Take screenshots of popup until it doesn't equal blankScreenshot (or we
+  // time out).
+  popup.getScreenshot(1000, 1000).onsuccess = function(e) {
+    var fr = new FileReader();
+    fr.onloadend = function() {
+      if (!arrayBuffersEqual(blankScreenshotArrayBuffer, fr.result)) {
+        ok(true, "Finally got a non-blank screenshot.");
+        SimpleTest.finish();
+        return;
+      }
+
+      SimpleTest.executeSoon(function() { test2(popup, blankScreenshot) });
+    };
+    fr.readAsArrayBuffer(e.target.result);
+  };
+}
+
+addEventListener('testready', runTest);