Media element: avoid v8 allocations in hasPendingActivity().

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

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights
  * reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 265 matching lines @@
     case WebMediaPlayer::PreloadMetaData:
       return "metadata";
     case WebMediaPlayer::PreloadAuto:
       return "auto";
   }
 
   NOTREACHED();
   return String();
 }
 
+class DisablePlaybackPositionUpdateScope {
+  STACK_ALLOCATED();
+
+ public:
+  DisablePlaybackPositionUpdateScope(bool* flag)
+      : m_flag(flag), m_value(*flag) {
+    *m_flag = false;
+  }
+
+  ~DisablePlaybackPositionUpdateScope() { *m_flag = m_value; }
+
+ private:
+  bool* m_flag;
+  bool m_value;
+};
+
 }  // anonymous namespace
 
 class HTMLMediaElement::AutoplayHelperClientImpl
     : public AutoplayExperimentHelper::Client {
  public:
   static AutoplayHelperClientImpl* create(HTMLMediaElement* element) {
     return new AutoplayHelperClientImpl(element);
   }
 
   virtual ~AutoplayHelperClientImpl();
@@ skipping 3155 matching lines @@
   // when looking for a resource to load, before networkState has reached to
   // kNetworkLoading.
   if (m_shouldDelayLoadEvent)
     return true;
 
   // When networkState is kNetworkLoading, progress and stalled events may be
   // fired.
   if (m_networkState == kNetworkLoading)
     return true;
 
-  // When playing or if playback may continue, timeupdate events may be fired.
-  if (couldPlayIfEnoughData())
-    return true;
+  {
+    // Disable potential updating of playback position, as that will
+    // require v8 allocations; not allowed while GCing
+    // (hasPendingActivity() is called during a v8 GC.)
+    DisablePlaybackPositionUpdateScope scope(

[haraken, 2016/11/16 06:47:26]

Can we use  AutoReset?

[sof, 2016/11/16 08:11:16]

Thanks, I'd forgotten about TemporaryChange<> / AutoReset<> being available.

+        &m_officialPlaybackPositionNeedsUpdate);
+
+    // When playing or if playback may continue, timeupdate events may be fired.
+    if (couldPlayIfEnoughData())
+      return true;
+  }
 
   // When the seek finishes timeupdate and seeked events will be fired.
   if (m_seeking)
     return true;
 
   // When connected to a MediaSource, e.g. setting MediaSource.duration will
   // cause a durationchange event to be fired.
   if (m_mediaSource)
     return true;
 
@@ skipping 718 matching lines @@
 
 IntRect HTMLMediaElement::AutoplayHelperClientImpl::absoluteBoundingBoxRect()
     const {
   IntRect result;
   if (LayoutObject* object = m_element->layoutObject())
     result = object->absoluteBoundingBoxRect();
   return result;
 }
 
 }  // namespace blink