UseCounter: Introduce UseCounter::Observer for layout tests

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
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY GOOGLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef UseCounter_h
 #define UseCounter_h
 
+#include <v8.h>
 #include "core/CSSPropertyNames.h"
 #include "core/CoreExport.h"
 #include "core/css/parser/CSSParserMode.h"
+#include "platform/heap/GarbageCollected.h"
+#include "platform/heap/HeapAllocator.h"
 #include "platform/weborigin/KURL.h"
 #include "wtf/BitVector.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/text/WTFString.h"
-#include <v8.h>
 
 namespace blink {
 
 class CSSStyleSheet;
 class Document;
 class EnumerationHistogram;
 class ExecutionContext;
 class Frame;
 class StyleSheetContents;
 
 // UseCounter is used for counting the number of times features of
 // Blink are used on real web pages and help us know commonly
 // features are used and thus when it's safe to remove or change them.
 //
 // The Chromium Content layer controls what is done with this data.
 //
 // For instance, in Google Chrome, these counts are submitted anonymously
 // through the UMA histogram recording system in Chrome for users who have the
 // "Automatically send usage statistics and crash reports to Google" setting
 // enabled:
 // http://www.google.com/chrome/intl/en/privacy.html
-
+//
+// Changes on UseCounter are observable by UseCounter::Observer.
 class CORE_EXPORT UseCounter {
   DISALLOW_NEW();
   WTF_MAKE_NONCOPYABLE(UseCounter);
 
  public:
   enum Context {
     DefaultContext,
     // Counters for SVGImages (lifetime independent from other pages).
     SVGImageContext
   };
@@ skipping 1391 matching lines @@
     V8DeprecatedStorageQuota_RequestQuota_Method = 1811,
     V8FileReaderSync_Constructor = 1812,
 
     // 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.
   };
 
+  // An interface to observe UseCounter changes. Note that this is never
+  // notified when the counter is disabled by |m_muteCount| or
+  // |m_disableReporting|.
+  class Observer : public GarbageCollected<Observer> {
+   public:
+    // Notified when a feature is counted for the first time. This should return
+    // true if it no longer needs to observe changes so that the counter can
+    // remove a reference to the observer and stop notifications.
+    virtual bool onCountFeature(Feature) = 0;
+
+    DEFINE_INLINE_VIRTUAL_TRACE() {}
+  };
+
   // "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);
 
+  // Adds an observer to Document's UseCounter. UseCounter retains a reference
+  // to the observer.
+  static void addObserver(Document&, Observer*);
+
   // Invoked when a new document is loaded into the main frame of the page.
   void didCommitLoad(KURL);
 
   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
   // reporting disabled.
   bool hasRecordedMeasurement(Feature) const;
 
+  DECLARE_TRACE();
+
  private:
+  // Notifies that a feature is newly counted to |m_observers|. This shouldn't
+  // be called when the counter is disabled by |m_muteCount| or
+  // |m_disableReporting|.
+  void notifyFeatureCounted(Feature);
+
   EnumerationHistogram& featuresHistogram() const;
   EnumerationHistogram& cssHistogram() const;
 
   // If non-zero, ignore all 'count' calls completely.
   unsigned m_muteCount;
 
   // If true, disable reporting all histogram entries.
   bool m_disableReporting;
 
   // The scope represented by this UseCounter instance.
   Context m_context;
 
   // Track what features/properties have been reported to the (non-legacy)
   // histograms.
   BitVector m_featuresRecorded;
   BitVector m_CSSRecorded;
 
+  HeapHashSet<Member<Observer>> m_observers;
+
   // Encapsulates the work to preserve the old "FeatureObserver" histogram with
   // original semantics
   // TODO(rbyers): remove this - http://crbug.com/676837
   class CORE_EXPORT LegacyCounter {
    public:
     LegacyCounter();
     ~LegacyCounter();
     void countFeature(Feature);
     void countCSS(CSSPropertyID);
     void updateMeasurements();
 
    private:
     // 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