Prevent more script-observable cases of HTMLMediaElement GC

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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 3505 matching lines @@
         renderer()->updateFromElement();
 
     stopPeriodicTimers();
     cancelPendingEventsAndCallbacks();
 
     m_asyncEventQueue->close();
 }
 
 bool HTMLMediaElement::hasPendingActivity() const
 {
-    return (hasAudio() && isPlaying()) || m_asyncEventQueue->hasPendingEvents();
+    // After the document becomes inactive, no events can ever be fired.
+    if (!document().isActive()) {
+        ASSERT(!m_asyncEventQueue->hasPendingEvents());
+        return false;
+    }
+
+    // The delaying-the-load-event flag is set by resource selection algorithm when looking for a
+    // resource to load, before networkState has reached to NETWORK_LOADING.
+    if (m_shouldDelayLoadEvent)
+        return true;
+
+    // When networkState is NETWORK_LOADING, progress and stalled events may be fired.
+    if (m_networkState == NETWORK_LOADING)
+        return true;
+
+    // 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;
+
+    // Wait for any pending events to be fired.
+    if (m_asyncEventQueue->hasPendingEvents())
+        return true;
+
+    return false;
 }
 
 void HTMLMediaElement::contextDestroyed()
 {
     // With Oilpan the ExecutionContext is weakly referenced from the media
     // controller and so it will clear itself on destruction.
 #if !ENABLE(OILPAN)
     if (m_mediaController)
         m_mediaController->clearExecutionContext();
 #endif
@@ skipping 472 matching lines @@
 
 #if ENABLE(WEB_AUDIO)
 void HTMLMediaElement::clearWeakMembers(Visitor* visitor)
 {
     if (!visitor->isAlive(m_audioSourceNode) && audioSourceProvider())
         audioSourceProvider()->setClient(0);
 }
 #endif
 
 }