Change CSSParserContext to have a Document handle (vs UseCounter).

third_party/WebKit/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 1444 matching lines @@
     CSSValueOnDemand = 1802,
     ServiceWorkerNavigationPreload = 1803,
 
     // Add new features immediately above this line. Don't change assigned
     // numbers of any item, and don't reuse removed slots.
     // Also, run update_use_counter_feature_enum.py in
     // chromium/src/tools/metrics/histograms/ to update the UMA mapping.
     NumberOfFeatures,  // This enum value must be last.
   };
 
+  static const Document* singleOwnerDocument(const StyleSheetContents*);
+  static const Document* singleOwnerDocument(const CSSStyleSheet*);

[haraken, 2017/02/08 01:40:00]

I'd move these methods to StyleSheetContents (or somewhere in core/style/).

[Bret, 2017/02/09 01:53:33]

Done. I moved these into their own class files (StyleSheetContents and
CSSStyleSheet respectively).

+
   // "count" sets the bit for this feature to 1. Repeated calls are ignored.
   static void count(const Frame*, Feature);
   static void count(const Document&, Feature);
   static void count(ExecutionContext*, Feature);
 
   void count(CSSParserMode, CSSPropertyID);
   void count(Feature);
 
   // Count only features if they're being used in an iframe which does not
   // have script access into the top level document.
   static void countCrossOriginIframe(const Document&, Feature);
 
   // Return whether the Feature was previously counted for this document.
   // NOTE: only for use in testing.
   static bool isCounted(Document&, Feature);
   // Return whether the CSSPropertyID was previously counted for this document.
   // NOTE: only for use in testing.
   static bool isCounted(Document&, const String&);
   bool isCounted(CSSPropertyID unresolvedProperty);
 
   // Invoked when a new document is loaded into the main frame of the page.
   void didCommitLoad(KURL);
 
-  static UseCounter* getFrom(const Document*);
-  static UseCounter* getFrom(const CSSStyleSheet*);
-  static UseCounter* getFrom(const StyleSheetContents*);
-
   static int mapCSSPropertyIdToCSSSampleIdForHistogram(CSSPropertyID);
 
   // When muted, all calls to "count" functions are ignoed.  May be nested.
   void muteForInspector();
   void unmuteForInspector();
 
   void recordMeasurement(Feature);
 
   // Return whether the feature has been seen since the last page load
   // (except when muted).  Does include features seen in documents which have
@@ skipping 33 matching lines @@
     // Tracks what features/properties need to be reported to the legacy
     // histograms.
     BitVector m_featureBits;
     BitVector m_CSSBits;
   } m_legacyCounter;
 };
 
 }  // namespace blink
 
 #endif  // UseCounter_h