Reenable feature policy control over fullscreen

third_party/WebKit/LayoutTests/fullscreen/full-screen-iframe-legacy.html

-<p>HTMLVideoElement.webkitEnterFullScreen() in an iframe requires the allowfullscreen attribute</p>
+<p>HTMLVideoElement.webkitEnterFullScreen() in a same-origin iframe does not require the allowfullscreen attribute</p>
 <script src="full-screen-test.js"></script>
 <script src="../media/media-file.js"></script>
 <script>
 var frame, video;
 
 function canplaythrough() {
     testExpected("video.webkitDisplayingFullscreen", false);
     runWithKeyDown(function() {
         video.webkitEnterFullScreen();
     });
-    waitForEventAndEnd(frame.contentDocument, "webkitfullscreenerror");
+    waitForEventAndEnd(frame.contentDocument, "webkitfullscreenchange");
 }
 
 function runTest() {
     frame = document.getElementById("frame");
     video = frame.contentDocument.querySelector("video");
     video.src = findMediaFile("video", "../../media/content/test");
     video.addEventListener("canplaythrough", canplaythrough);
 }
 </script>
 <iframe id="frame" src="resources/legacy.html" onload="runTest()" width="336" height="256">
 </iframe>