Measure how often Attr needs its associated Element

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 291 matching lines @@
         WindowOrientation = 285,
         DOMStringListContains = 286,
         DocumentCaptureEvents = 287,
         DocumentReleaseEvents = 288,
         WindowCaptureEvents = 289,
         WindowReleaseEvents = 290,
         PrefixedGamepad = 291,
         ElementAnimateKeyframeListEffectObjectTiming = 292,
         ElementAnimateKeyframeListEffectDoubleTiming = 293,
         ElementAnimateKeyframeListEffectNoTiming = 294,
+        AttrGetValueNeedsElement = 295,
+        AttrSetValueNeedsElement = 296,
+        AttrChildrenChanged = 297,
+        AttrNodeValue = 298,
         // Add new features immediately above this line. Don't change assigned
         // numbers of any item, and don't reuse removed slots.
         NumberOfFeatures, // This enum value must be last.
     };
 
     // "count" sets the bit for this feature to 1. Repeated calls are ignored.
     static void count(const Document&, Feature);
     static void count(const ExecutionContext*, Feature);
     void count(CSSParserContext, CSSPropertyID);
     void count(Feature);
@@ skipping 42 matching lines @@
 
     void updateMeasurements();
 
     OwnPtr<BitVector> m_countBits;
     BitVector m_CSSFeatureBits;
 };
 
 } // namespace WebCore
 
 #endif // UseCounter_h