Only execute default actions on trusted events.

LayoutTests/fast/events/option-tab.html

 <p>This tests that option-tab moves you from a text field to a link, but plain old tab does not.</p>
 <p>Note: Option is the Mac name for what other platforms call Alt.</p>
 <input id="textField" type=text> <a onfocus="window.linkFocused = true" href="http://www.apple.com">link</a>
 <input id="searchField" type=search> <a onfocus="window.linkFocused = true" href="http://www.apple.com">link</a>
 <pre id="console">
 </pre>
 <script>
 
 if (window.testRunner)
     testRunner.dumpAsText();
 
 function test(fieldId)
 {
     window.linkFocused = false;
     document.getElementById(fieldId).focus();
-    var event = document.createEvent("KeyboardEvents");
-    event.initKeyboardEvent("keydown", true, true, document.defaultView, "U+0009", 0, false, true, false, false, false);
-    document.getElementById(fieldId).dispatchEvent(event);
+
+    if (window.eventSender)
+        eventSender.keyDown('\u0009', ["altKey"]);
+
     if (window.linkFocused)
         document.getElementById("console").innerHTML += "SUCCESS: Option-tab did tab to the link (" + fieldId + ").\n";
     else
         document.getElementById("console").innerHTML += "FAIL: Option-tab did not tab to the link (" + fieldId + ").\n";
 
     window.linkFocused = false;
     document.getElementById(fieldId).focus();
-    event = document.createEvent("KeyboardEvents");
-    event.initKeyboardEvent("keydown", true, true, document.defaultView, "U+0009", 0, false, false, false, false, false);
-    document.getElementById(fieldId).dispatchEvent(event);
+
+    if (window.eventSender)
+        eventSender.keyDown('\u0009', []);
+
     if (window.linkFocused)
         document.getElementById("console").innerHTML += "FAIL: Plain old tab did tab to the link (" + fieldId + ").\n";
     else
         document.getElementById("console").innerHTML += "SUCCESS: Plain old tab did not tab to the link (" + fieldId + ").\n";
 }
 
 test("textField");
 test("searchField");
 
 </script>