Add Event.isTrusted support

LayoutTests/fast/events/event-trusted.html

+<input id="clitty-click" type="checkbox"/>
+<div id="console"/>
+<script src="../../resources/js-test.js"></script>
+<script>
+    description("This tests that isTrusted returns the correct value under certain situations.")

[tkent, 2015/07/16 03:29:37]

nit: should remove the top-level 4 space indentation.  It is not helpful.

[dtapuska, 2015/07/16 14:48:21]

Done.

+
+    var redispatched = false;
+
+    function createAndInitEvent() {
+        var e = document.createEvent('Event');
+        e.initEvent(false, false, false);
+        return e;
+    }
+
+    shouldBeFalse("document.createEvent('Event').isTrusted");
+    shouldBeFalse("createAndInitEvent().isTrusted");
+
+    function originalDispatch(e) {
+        originalEvent = e;
+    }
+
+    function redispatch(e) {
+        redispatched = true;   
+    }     
+
+    var element = document.getElementById("clitty-click");
+    if (window.eventSender) {
+        element.addEventListener('click', originalDispatch);
+        element.addEventListener('focus', function (e) {
+            event = e;
+            shouldBeTrue("event.isTrusted");
+        });
+        eventSender.mouseMoveTo(element.offsetLeft, element.offsetTop);
+        eventSender.mouseDown();
+        eventSender.mouseUp();
+
+        shouldBeTrue("originalEvent.isTrusted");
+        element.removeEventListener('click', originalDispatch);
+        element.addEventListener('click', redispatch);
+
+        element.dispatchEvent(originalEvent);
+        shouldBeTrue("redispatched");
+        shouldBeFalse("originalEvent.isTrusted");
+    }
+
+</script>