--- a/editor/libeditor/moz.build
+++ b/editor/libeditor/moz.build
@@ -6,16 +6,18 @@
 
 MOCHITEST_MANIFESTS += [
     'tests/browserscope/mochitest.ini',
     'tests/mochitest.ini',
 ]
 
 MOCHITEST_CHROME_MANIFESTS += ['tests/chrome.ini']
 
+BROWSER_CHROME_MANIFESTS += ['tests/browser.ini']
+
 UNIFIED_SOURCES += [
     'ChangeAttributeTxn.cpp',
     'ChangeStyleTxn.cpp',
     'CreateElementTxn.cpp',
     'DeleteNodeTxn.cpp',
     'DeleteRangeTxn.cpp',
     'DeleteTextTxn.cpp',
     'EditAggregateTxn.cpp',

new file mode 100644
--- /dev/null
+++ b/editor/libeditor/tests/browser.ini
@@ -0,0 +1,3 @@
+[browser_bug629172.js]
+skip-if = toolkit == 'android'
+support-files = bug629172.html

new file mode 100644
--- /dev/null
+++ b/editor/libeditor/tests/browser_bug629172.js
@@ -0,0 +1,106 @@
+add_task(function*() {
+  yield new Promise(resolve => waitForFocus(resolve, window));
+
+  const kPageURL = "http://example.org/browser/editor/libeditor/tests/bug629172.html";
+  yield BrowserTestUtils.withNewTab({
+    gBrowser,
+    url: kPageURL
+  }, function*(aBrowser) {
+    yield ContentTask.spawn(aBrowser, {}, function*() {
+      var window = content.window.wrappedJSObject;
+      var document = window.document;
+
+      // Note: Using the with keyword, we would have been able to write this as:
+      //
+      // with (window) {
+      //   Screenshots = {};
+      //   // so on
+      // }
+      //
+      // However, browser-chrome tests are somehow forced to run in strict mode,
+      // which doesn't permit the usage of the with keyword, turning the following
+      // into the ugliest test you've ever seen.  :(
+      var LTRRef = document.getElementById("ltr-ref");
+      var RTLRef = document.getElementById("rtl-ref");
+      window.Screenshots = {};
+
+      // generate the reference screenshots
+      LTRRef.style.display = "";
+      document.body.clientWidth;
+      window.Screenshots.ltr = window.snapshotWindow(window);
+      LTRRef.parentNode.removeChild(LTRRef);
+      RTLRef.style.display = "";
+      document.body.clientWidth;
+      window.Screenshots.rtl = window.snapshotWindow(window);
+      RTLRef.parentNode.removeChild(RTLRef);
+      window.Screenshots.get = function(dir, flip) {
+        if (flip) {
+          return this[dir == "rtl" ? "ltr" : "rtl"];
+        } else {
+          return this[dir];
+        }
+      };
+    });
+
+    function simulateCtrlShiftX(aBrowser) {
+      // In e10s, the keypress event will be dispatched to the content process,
+      // but in non-e10s it is handled by the browser UI code and hence won't
+      // reach the web page.  As a result, we need to observe the event in
+      // the content process only in e10s mode.
+      var waitForKeypressContent = BrowserTestUtils.waitForContentEvent(aBrowser, "keypress");
+      EventUtils.synthesizeKey("x", {accelKey: true, shiftKey: true});
+      if (gMultiProcessBrowser) {
+        return waitForKeypressContent;
+      }
+      return Promise.resolve();
+    }
+
+    function* testDirection(initialDir, aBrowser) {
+      yield ContentTask.spawn(aBrowser, {initialDir}, function({initialDir}) {
+        var window = content.window.wrappedJSObject;
+        var document = window.document;
+
+        var t = window.t = document.createElement("textarea");
+        t.setAttribute("dir", initialDir);
+        t.value = "test.";
+        window.inputEventCount = 0;
+        t.oninput = function() { window.inputEventCount++; };
+        document.getElementById("content").appendChild(t);
+        document.body.clientWidth;
+        var s1 = window.snapshotWindow(window);
+        ok(window.compareSnapshots(s1, window.Screenshots.get(initialDir, false), true)[0],
+           "Textarea should appear correctly before switching the direction (" + initialDir + ")");
+        t.focus();
+        is(window.inputEventCount, 0, "input event count must be 0 before");
+      });
+      yield simulateCtrlShiftX(aBrowser);
+      yield ContentTask.spawn(aBrowser, {initialDir}, function({initialDir}) {
+        var window = content.window.wrappedJSObject;
+
+        is(window.t.getAttribute("dir"), initialDir == "ltr" ? "rtl" : "ltr", "The dir attribute must be correctly updated");
+        is(window.inputEventCount, 1, "input event count must be 1 after");
+        window.t.blur();
+        var s2 = window.snapshotWindow(window);
+        ok(window.compareSnapshots(s2, window.Screenshots.get(initialDir, true), true)[0],
+           "Textarea should appear correctly after switching the direction (" + initialDir + ")");
+        window.t.focus();
+        is(window.inputEventCount, 1, "input event count must be 1 before");
+      });
+      yield simulateCtrlShiftX(aBrowser);
+      yield ContentTask.spawn(aBrowser, {initialDir}, function({initialDir}) {
+        var window = content.window.wrappedJSObject;
+
+        is(window.inputEventCount, 2, "input event count must be 2 after");
+        is(window.t.getAttribute("dir"), initialDir == "ltr" ? "ltr" : "rtl", "The dir attribute must be correctly updated");
+        window.t.blur();
+        var s3 = window.snapshotWindow(window);
+        ok(window.compareSnapshots(s3, window.Screenshots.get(initialDir, false), true)[0],
+           "Textarea should appear correctly after switching back the direction (" + initialDir + ")");
+        window.t.parentNode.removeChild(window.t);
+      });
+    }
+
+    yield testDirection("ltr", aBrowser);
+    yield testDirection("rtl", aBrowser);
+  });
+});

new file mode 100644
--- /dev/null
+++ b/editor/libeditor/tests/bug629172.html
@@ -0,0 +1,15 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<script type="text/javascript" src="/tests/SimpleTest/WindowSnapshot.js"></script>
+<style>
+textarea { resize: none }
+</style>
+</head>
+<body>
+<div id="content">
+<textarea id="ltr-ref" style="display: none">test.</textarea>
+<textarea id="rtl-ref" style="display: none; direction: rtl">test.</textarea>
+</div
+</body>
+</html>

--- a/editor/libeditor/tests/mochitest.ini
+++ b/editor/libeditor/tests/mochitest.ini
@@ -97,18 +97,16 @@ skip-if = toolkit == 'android'
 skip-if = toolkit == 'android'
 [test_bug612128.html]
 [test_bug612447.html]
 [test_bug620906.html]
 skip-if = toolkit == 'android' #TIMED_OUT
 [test_bug622371.html]
 skip-if = toolkit == 'android' #bug 957797
 [test_bug625452.html]
-[test_bug629172.html]
-skip-if = toolkit == 'android' || e10s
 [test_bug629845.html]
 [test_bug638596.html]
 [test_bug640321.html]
 skip-if = android_version == '18' # bug 1147989
 [test_bug641466.html]
 [test_bug645914.html]
 [test_bug668599.html]
 [test_bug674770-1.html]

deleted file mode 100644
--- a/editor/libeditor/tests/test_bug629172.html
+++ /dev/null
@@ -1,88 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=629172
--->
-<head>
-  <title>Test for Bug 629172</title>
-  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <script type="text/javascript" src="/tests/SimpleTest/EventUtils.js"></script>
-  <script type="text/javascript" src="/tests/SimpleTest/WindowSnapshot.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-</head>
-<body>
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=629172">Mozilla Bug 629172</a>
-<p id="display"></p>
-<div id="content">
-<textarea id="ltr-ref" style="display: none">test.</textarea>
-<textarea id="rtl-ref" style="display: none; direction: rtl">test.</textarea>
-</div>
-<pre id="test">
-<script type="application/javascript">
-
-/** Test for Bug 629172 **/
-SimpleTest.waitForExplicitFinish();
-SimpleTest.waitForFocus(function() {
-  var LTRRef = document.getElementById("ltr-ref");
-  var RTLRef = document.getElementById("rtl-ref");
-  var Screenshots = {};
-
-  // generate the reference screenshots
-  LTRRef.style.display = "";
-  document.body.clientWidth;
-  Screenshots.ltr = snapshotWindow(window);
-  LTRRef.parentNode.removeChild(LTRRef);
-  RTLRef.style.display = "";
-  document.body.clientWidth;
-  Screenshots.rtl = snapshotWindow(window);
-  RTLRef.parentNode.removeChild(RTLRef);
-  Screenshots.get = function(dir, flip) {
-    if (flip) {
-      return this[dir == "rtl" ? "ltr" : "rtl"];
-    } else {
-      return this[dir];
-    }
-  };
-
-  function testDirection(initialDir) {
-    var t = document.createElement("textarea");
-    t.setAttribute("dir", initialDir);
-    t.value = "test.";
-    var inputEventCount = 0;
-    t.oninput = function() { inputEventCount++; };
-    document.getElementById("content").appendChild(t);
-    document.body.clientWidth;
-    var s1 = snapshotWindow(window);
-    ok(compareSnapshots(s1, Screenshots.get(initialDir, false), true)[0],
-       "Textarea should appear correctly before switching the direction (" + initialDir + ")");
-    t.focus();
-    is(inputEventCount, 0, "input event count must be 0 before");
-    synthesizeKey("x", {accelKey: true, shiftKey: true});
-    is(t.getAttribute("dir"), initialDir == "ltr" ? "rtl" : "ltr", "The dir attribute must be correctly updated");
-    is(inputEventCount, 1, "input event count must be 1 after");
-    t.blur();
-    var s2 = snapshotWindow(window);
-    ok(compareSnapshots(s2, Screenshots.get(initialDir, true), true)[0],
-       "Textarea should appear correctly after switching the direction (" + initialDir + ")");
-    t.focus();
-    is(inputEventCount, 1, "input event count must be 1 before");
-    synthesizeKey("x", {accelKey: true, shiftKey: true});
-    is(inputEventCount, 2, "input event count must be 2 after");
-    is(t.getAttribute("dir"), initialDir == "ltr" ? "ltr" : "rtl", "The dir attribute must be correctly updated");
-    t.blur();
-    var s3 = snapshotWindow(window);
-    ok(compareSnapshots(s3, Screenshots.get(initialDir, false), true)[0],
-       "Textarea should appear correctly after switching back the direction (" + initialDir + ")");
-    t.parentNode.removeChild(t);
-  }
-
-  testDirection("ltr");
-  testDirection("rtl");
-
-  SimpleTest.finish();
-});
-
-</script>
-</pre>
-</body>
-</html>