Media: fix memory leak because of the document holding on an EventListener.

third_party/WebKit/Source/core/html/shadow/MediaControlsOrientationLockDelegate.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "MediaControlsOrientationLockDelegate.h"
 
 #include "core/events/Event.h"
 #include "core/frame/ScreenOrientationController.h"
 #include "core/html/HTMLVideoElement.h"
 #include "core/page/ChromeClient.h"
@@ skipping 57 matching lines @@
   videoElement().addEventListener(EventTypeNames::webkitfullscreenchange, this,
                                   true);
   videoElement().addEventListener(EventTypeNames::loadedmetadata, this, true);
 }
 
 bool MediaControlsOrientationLockDelegate::operator==(
     const EventListener& other) const {
   return this == &other;
 }
 
+void MediaControlsOrientationLockDelegate::detach() {
+  document().removeEventListener(EventTypeNames::fullscreenchange, this, true);

[Zhiqiang Zhang (Slow), 2017/03/01 16:22:36]

Should we also remove the listeners from the video element? In case the page
adds/removes the element to/from the page multiple times, we are creating many
MediaControl objects and this will prevent the
MediaControlsOrientationLockDelegate objects to be gc-ed.

[mlamouri (slow - plz ping), 2017/03/01 20:22:33]

Good point :) Though, the approach the first iteration was taking didn't work so
I had to change. 

+}
+
 void MediaControlsOrientationLockDelegate::maybeLockOrientation() {
   DCHECK(m_state != State::MaybeLockedFullscreen);
 
   if (videoElement().getReadyState() == HTMLMediaElement::kHaveNothing) {
     recordMetadataAvailability(MetadataAvailabilityMetrics::Missing);
     m_state = State::PendingMetadata;
     return;
   }
 
   if (m_state == State::PendingMetadata)
@@ skipping 104 matching lines @@
   NOTREACHED();
   return WebScreenOrientationLockLandscape;
 }
 
 DEFINE_TRACE(MediaControlsOrientationLockDelegate) {
   EventListener::trace(visitor);
   visitor->trace(m_videoElement);
 }
 
 }  // namespace blink