Fixing a crash in MediaCustomControlsFullscreenDetector when the page is destroyed

third_party/WebKit/Source/core/html/MediaCustomControlsFullscreenDetector.cpp

 // Copyright 2017 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 "core/html/MediaCustomControlsFullscreenDetector.h"
 
 #include "core/dom/Fullscreen.h"
 #include "core/dom/TaskRunnerHelper.h"
 #include "core/events/Event.h"
 #include "core/html/HTMLVideoElement.h"
 #include "core/layout/IntersectionGeometry.h"
 
 namespace blink {
 
 namespace {
 
 constexpr double kCheckFullscreenIntervalSeconds = 1.0f;
 constexpr float kMostlyFillViewportThresholdOfOccupationProportion = 0.85f;
 constexpr float kMostlyFillViewportThresholdOfVisibleProportion = 0.75f;
 
 }  // anonymous namespace
 
 MediaCustomControlsFullscreenDetector::MediaCustomControlsFullscreenDetector(
     HTMLVideoElement& video)
     : EventListener(CPPEventListenerType),
+      ContextLifecycleObserver(nullptr),
       m_videoElement(video),
       m_checkViewportIntersectionTimer(
           TaskRunnerHelper::get(TaskType::Unthrottled, &video.document()),
           this,
           &MediaCustomControlsFullscreenDetector::
               onCheckViewportIntersectionTimerFired) {
   videoElement().addEventListener(EventTypeNames::DOMNodeInsertedIntoDocument,
                                   this, false);
   videoElement().addEventListener(EventTypeNames::DOMNodeRemovedFromDocument,
                                   this, false);
 
   videoElement().addEventListener(EventTypeNames::loadedmetadata, this, true);
 }
 
 bool MediaCustomControlsFullscreenDetector::operator==(
     const EventListener& other) const {
   return this == &other;
 }
 
 void MediaCustomControlsFullscreenDetector::attach() {
+  setContext(&videoElement().document());
   videoElement().document().addEventListener(
       EventTypeNames::webkitfullscreenchange, this, true);
   videoElement().document().addEventListener(EventTypeNames::fullscreenchange,
                                              this, true);
 }
 
 void MediaCustomControlsFullscreenDetector::detach() {
+  setContext(nullptr);
   videoElement().document().removeEventListener(
       EventTypeNames::webkitfullscreenchange, this, true);
   videoElement().document().removeEventListener(
       EventTypeNames::fullscreenchange, this, true);
+  m_checkViewportIntersectionTimer.stop();
 }
 
 bool MediaCustomControlsFullscreenDetector::computeIsDominantVideoForTests(
     const IntRect& targetRect,
     const IntRect& rootRect,
     const IntRect& intersectionRect) {
   if (targetRect.isEmpty() || rootRect.isEmpty())
     return false;
 
   const float xOccupationProportion =
@@ skipping 52 matching lines @@
     if (videoElement().webMediaPlayer())
       videoElement().webMediaPlayer()->setIsEffectivelyFullscreen(false);
 
     return;
   }
 
   m_checkViewportIntersectionTimer.startOneShot(kCheckFullscreenIntervalSeconds,
                                                 BLINK_FROM_HERE);
 }
 
+void MediaCustomControlsFullscreenDetector::contextDestroyed(
+    ExecutionContext*) {
+  if (videoElement().webMediaPlayer())
+    videoElement().webMediaPlayer()->setIsEffectivelyFullscreen(false);
+
+  detach();
+}
+
 void MediaCustomControlsFullscreenDetector::
     onCheckViewportIntersectionTimerFired(TimerBase*) {
   DCHECK(isVideoOrParentFullscreen());
   IntersectionGeometry geometry(nullptr, videoElement(), Vector<Length>(),
                                 true);
   geometry.computeGeometry();
 
   bool isDominant = computeIsDominantVideoForTests(
       geometry.targetIntRect(), geometry.rootIntRect(),
       geometry.intersectionIntRect());
 
   if (videoElement().webMediaPlayer())
     videoElement().webMediaPlayer()->setIsEffectivelyFullscreen(isDominant);
 }
 
 bool MediaCustomControlsFullscreenDetector::isVideoOrParentFullscreen() {
   Element* fullscreenElement =
       Fullscreen::currentFullScreenElementFrom(videoElement().document());
   if (!fullscreenElement)
     return false;
 
   return fullscreenElement->contains(&videoElement());
 }
 
 DEFINE_TRACE(MediaCustomControlsFullscreenDetector) {
   EventListener::trace(visitor);
+  ContextLifecycleObserver::trace(visitor);
   visitor->trace(m_videoElement);
 }
 
 }  // namespace blink