Use a new Supplement constructor for Supplement<Document> (Part 1)

third_party/WebKit/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 48 matching lines @@
   }
 
   void updateSelectorMatches(const Vector<String>& removedSelectors,
                              const Vector<String>& addedSelectors);
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   explicit CSSSelectorWatch(Document&);
   void callbackSelectorChangeTimerFired(TimerBase*);
-  Document& document() const { return *m_document; }
-
-  Member<Document> m_document;
 
   HeapVector<Member<StyleRule>> m_watchedCallbackSelectors;
 
   // Maps a CSS selector string with a -webkit-callback property to the number
   // of matching ComputedStyle objects in this document.
   HashCountedSet<String> m_matchingCallbackSelectors;
   // Selectors are relative to m_matchingCallbackSelectors's contents at
   // the previous call to selectorMatchChanged.
   HashSet<String> m_addedSelectors;
   HashSet<String> m_removedSelectors;
 
   TaskRunnerTimer<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;
 
   friend class CSSSelectorWatchTest;
 };
 
 }  // namespace blink
 
 #endif  // CSSSelectorWatch_h