Remove Attr child nodes (making Attr a Node, not a ContainerNode)

Source/core/frame/UseCounter.h

 /*
  * Copyright (C) 2012 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:
  * 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 500 matching lines @@
         InputTypeSubmit = 591,
         InputTypeSubmitWithValue = 592,
         // The above items are available in M40 branch.
 
         SetReferrerPolicy = 593,
         MouseEventWhich = 595,
         UIEventCharCode = 596,
         UIEventKeyCode = 597,
         UIEventWhich = 598,
         TextWholeText = 599,
-        AttrChildAccess = 600,
-        AttrChildChange = 601,
         NotificationCloseEvent = 603,
         StyleMedia = 606,
         StyleMediaType = 607,
         StyleMediaMatchMedium = 608,
         MixedContentPresent = 609,
         MixedContentBlockable = 610,
         MixedContentAudio = 611,
         MixedContentDownload = 612,
         MixedContentFavicon = 613,
         MixedContentImage = 614,
@@ skipping 274 matching lines @@
 
     bool hasRecordedMeasurement(Feature feature) const { return m_countBits.hasRecordedMeasurement(feature); }
 
     CountBits m_countBits;
     BitVector m_CSSFeatureBits;
 };
 
 } // namespace blink
 
 #endif // UseCounter_h