Add metrics for style update time before FCP.

third_party/WebKit/Source/core/timing/PerformanceTiming.h

 /*
  * Copyright (C) 2010 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 89 matching lines @@
   // where the page's primary content is visible.
   unsigned long long firstMeaningfulPaint() const;
 
   unsigned long long parseStart() const;
   unsigned long long parseStop() const;
   unsigned long long parseBlockedOnScriptLoadDuration() const;
   unsigned long long parseBlockedOnScriptLoadFromDocumentWriteDuration() const;
   unsigned long long parseBlockedOnScriptExecutionDuration() const;
   unsigned long long parseBlockedOnScriptExecutionFromDocumentWriteDuration()
       const;
-
-  // Microseconds spend parsing author style sheets before the first contentful
-  // paint.
   unsigned long long authorStyleSheetParseDurationBeforeFCP() const;
+  unsigned long long updateStyleDurationBeforeFCP() const;
 
   ScriptValue toJSONForBinding(ScriptState*) const;
 
   DECLARE_VIRTUAL_TRACE();
 
   unsigned long long monotonicTimeToIntegerMilliseconds(double) const;
   double integerMillisecondsToMonotonicTime(unsigned long long) const;
 
  private:
   explicit PerformanceTiming(LocalFrame*);
 
   const DocumentTiming* documentTiming() const;
   const CSSTiming* cssTiming() const;
   const DocumentParserTiming* documentParserTiming() const;
   const PaintTiming* paintTiming() const;
   DocumentLoader* documentLoader() const;
   DocumentLoadTiming* documentLoadTiming() const;
   ResourceLoadTiming* resourceLoadTiming() const;
 };
 
 }  // namespace blink
 
 #endif  // PerformanceTiming_h