Media Controls: do not use events but C++ callbacks for insertion/removal from document.

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 51 matching lines @@
 }  // anonymous namespace
 
 MediaControlsOrientationLockDelegate::MediaControlsOrientationLockDelegate(
     HTMLVideoElement& video)
     : EventListener(CPPEventListenerType), m_videoElement(video) {
   if (videoElement().isConnected())
     attach();
 }
 
 void MediaControlsOrientationLockDelegate::attach() {
+  DCHECK(videoElement().isConnected());
+
   document().addEventListener(EventTypeNames::fullscreenchange, this, true);
   videoElement().addEventListener(EventTypeNames::webkitfullscreenchange, this,
                                   true);
   videoElement().addEventListener(EventTypeNames::loadedmetadata, this, true);
 }
 
 void MediaControlsOrientationLockDelegate::detach() {
+  DCHECK(!videoElement().isConnected());
+
   document().removeEventListener(EventTypeNames::fullscreenchange, this, true);
   videoElement().removeEventListener(EventTypeNames::webkitfullscreenchange,
                                      this, true);
   videoElement().removeEventListener(EventTypeNames::loadedmetadata, this,
                                      true);
 }
 
 bool MediaControlsOrientationLockDelegate::operator==(
     const EventListener& other) const {
   return this == &other;
@@ skipping 116 matching lines @@
   NOTREACHED();
   return WebScreenOrientationLockLandscape;
 }
 
 DEFINE_TRACE(MediaControlsOrientationLockDelegate) {
   EventListener::trace(visitor);
   visitor->trace(m_videoElement);
 }
 
 }  // namespace blink