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

third_party/WebKit/Source/core/frame/UseCounter.h

Index: third_party/WebKit/Source/core/frame/UseCounter.h
diff --git a/third_party/WebKit/Source/core/frame/UseCounter.h b/third_party/WebKit/Source/core/frame/UseCounter.h
index 5579ffa5c0fd904b1f40c1d2a867a8d2e99a28ce..3f80ea5b2f6e6cf277aae6ab53d42b158b161795 100644
--- a/third_party/WebKit/Source/core/frame/UseCounter.h
+++ b/third_party/WebKit/Source/core/frame/UseCounter.h
@@ -1462,6 +1462,9 @@ class CORE_EXPORT UseCounter {
     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);
@@ -1485,10 +1488,6 @@ class CORE_EXPORT UseCounter {
   // 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.