Implement the unprefixed the Fullscreen API

LayoutTests/fullscreen/trusted-event.js

+// Invokes callback from a trusted event.
+// When testing manually, a button is added to the container.
+function trusted_event(callback, container)
+{
+    var document = container.ownerDocument;
+
+    if (window.testRunner) {
+        // Running under LayoutTests. Use timeout to be async.
+        setTimeout(function()
+        {
+            document.addEventListener("click", callback);
+            eventSender.mouseDown();
+            eventSender.mouseUp();
+            document.removeEventListener("click", callback);
+        }, 0);
+    } else {
+        // Running as manual test. Show a button to click.
+        var button = document.createElement("button");
+        button.textContent = "click to run test";
+        button.style.fontSize = "20px";
+        button.style.padding = "10px";
+        button.onclick = function()
+        {
+            callback();
+            button.onclick = null;
+            container.removeChild(button);
+        };
+        container.appendChild(button);
+    }
+}
+
+// Invokes element.requestFullscreen() from a trusted event.
+function trusted_request(element)
+{
+    var request = element.requestFullscreen.bind(element);
+    trusted_event(request, element.parentNode);
+}