Update MediaKeySession lifetime description to be Oilpan reality-based.

Source/core/dom/CSSSelectorWatch.h

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 20 matching lines @@
 #ifndef CSSSelectorWatch_h
 #define CSSSelectorWatch_h
 
 #include "core/css/StyleRule.h"
 #include "core/dom/DocumentSupplementable.h"
 #include "platform/Timer.h"
 #include "wtf/HashCountedSet.h"
 #include "wtf/HashSet.h"
 #include "wtf/RefPtr.h"
 #include "wtf/Vector.h"
-#include "wtf/WeakPtr.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class CSSSelectorWatch final : public NoBaseWillBeGarbageCollectedFinalized<CSSSelectorWatch>, public DocumentSupplement {
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(CSSSelectorWatch);
 public:
     virtual ~CSSSelectorWatch() { }
 
     static CSSSelectorWatch& from(Document&);
@@ skipping 25 matching lines @@
     Timer<CSSSelectorWatch> m_callbackSelectorChangeTimer;
 
     // When an element is reparented, the new location's style is evaluated after the expriation of the relayout timer.
     // We don't want to send redundant callbacks to the embedder, so this counter lets us wait another time around the event loop.
     int m_timerExpirations;
 };
 
 } // namespace blink
 
 #endif // CSSSelectorWatch_h