--- a/dom/browser-element/mochitest/browserElementTestHelpers.js
+++ b/dom/browser-element/mochitest/browserElementTestHelpers.js
@@ -60,16 +60,20 @@ const browserElementTestHelpers = {
   setEnabledPref: function(value) {
     this._setPref('dom.mozBrowserFramesEnabled', value);
   },
 
   setSelectionChangeEnabledPref: function(value) {
     this._setPref('selectioncaret.enabled', value);
   },
 
+  setAccessibleCaretEnabledPref: function(value) {
+    this._setPref('layout.accessiblecaret.enabled', value);
+  },
+
   getOOPByDefaultPref: function() {
     return this._getBoolPref("dom.ipc.browser_frames.oop_by_default");
   },
 
   addPermission: function() {
     this.lockTestReady();
     SpecialPowers.pushPermissions(
       [{'type': "browser", 'allow': 1, 'context': document}],

--- a/dom/browser-element/mochitest/browserElement_CopyPaste.js
+++ b/dom/browser-element/mochitest/browserElement_CopyPaste.js
@@ -16,16 +16,17 @@ var mm;
 var iframeOuter;
 var iframeInner;
 var state = 0;
 var stateMeaning;
 var defaultData;
 var pasteData;
 var focusScript;
 var createEmbededFrame = false;
+var testAccessibleCaret = false;
 
 function copyToClipboard(str) {
   gTextarea.value = str;
   SpecialPowers.wrap(gTextarea).editor.selectAll();
   SpecialPowers.wrap(gTextarea).editor.copy();
 }
 
 function getScriptForGetContent() {
@@ -155,47 +156,58 @@ function dispatchTest(e) {
                    "</body>" +
                    "<script>document.designMode='on';</script>" +
                    "</html>";
       stateMeaning = " (test: normal div with designMode:on)";
       focusScript = "var elt=content.document.getElementById('text');elt.focus();";
       break;
     default:
       if (createEmbededFrame || browserElementTestHelpers.getOOPByDefaultPref()) {
-        SimpleTest.finish();
+        if (testAccessibleCaret) {
+          SimpleTest.finish();
+          return;
+        } else {
+          testAccessibleCaret = true;
+          createEmbededFrame = false;
+          browserElementTestHelpers.setSelectionChangeEnabledPref(false);
+          browserElementTestHelpers.setAccessibleCaretEnabledPref(true);
+        }
       } else {
         createEmbededFrame = true;
+      }
 
-        // clean up and run test again.
-        document.body.removeChild(iframeOuter);
-        document.body.removeChild(gTextarea);
-        state = 0;
-        runTest();
-      }
+      // clean up and run test again.
+      document.body.removeChild(iframeOuter);
+      document.body.removeChild(gTextarea);
+      state = 0;
+      runTest();
       break;
   }
 }
 
 function isChildProcess() {
   return SpecialPowers.Cc["@mozilla.org/xre/app-info;1"]
                          .getService(SpecialPowers.Ci.nsIXULRuntime)
                          .processType != SpecialPowers.Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
 }
 
 function testSelectAll(e) {
   // Skip mozbrowser test if we're at child process.
   if (!isChildProcess()) {
-    iframeOuter.addEventListener("mozbrowserselectionstatechanged", function selectchangeforselectall(e) {
-      if (e.detail.states.indexOf('selectall') == 0) {
-        iframeOuter.removeEventListener("mozbrowserselectionstatechanged", selectchangeforselectall, true);
+    let eventName = testAccessibleCaret ? "mozbrowsercaretstatechanged" : "mozbrowserselectionstatechanged";
+    iframeOuter.addEventListener(eventName, function selectchangeforselectall(e) {
+      if (!e.detail.states || e.detail.states.indexOf('selectall') == 0) {
+        iframeOuter.removeEventListener(eventName, selectchangeforselectall, true);
         ok(true, "got mozbrowserselectionstatechanged event." + stateMeaning);
         ok(e.detail, "event.detail is not null." + stateMeaning);
         ok(e.detail.width != 0, "event.detail.width is not zero" + stateMeaning);
         ok(e.detail.height != 0, "event.detail.height is not zero" + stateMeaning);
-        ok(e.detail.states, "event.detail.state " + e.detail.states);
+        if (!testAccessibleCaret) {
+          ok(e.detail.states, "event.detail.state " + e.detail.states);
+        }
         SimpleTest.executeSoon(function() { testCopy1(e); });
       }
     }, true);
   }
 
   mm.addMessageListener('content-focus', function messageforfocus(msg) {
     mm.removeMessageListener('content-focus', messageforfocus);
     // test selectall command, after calling this the selectionstatechanged event should be fired.