[WIP] Add WebCore.UseCounter UMA to supercede FeatureObserver

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 42 matching lines @@
 // For instance, in Google Chrome, these counts are submitted
 // anonymously through the Histogram recording system in Chrome
 // for users who opt-in to "Usage Statistics" submission
 // during their install of Google Chrome:
 // http://www.google.com/chrome/intl/en/privacy.html
 
 class CORE_EXPORT UseCounter {
     DISALLOW_NEW();
     WTF_MAKE_NONCOPYABLE(UseCounter);
 public:
-    UseCounter();
-    ~UseCounter();
+    UseCounter()
+        : m_featuresReported(NumberOfFeatures)
+        , m_CSSFeaturesReported(lastUnresolvedCSSProperty + 1)
+    {}
 
     enum Feature {
         // Do not change assigned numbers of existing items: add new features
         // to the end of the list.
         PageDestruction = 0,
         PrefixedIndexedDB = 3,
         WorkerStart = 4,
         SharedWorkerStart = 5,
         UnprefixedIndexedDB = 9,
         OpenWebDatabase = 10,
@@ skipping 1155 matching lines @@
 
     // 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);
 
     void didCommitLoad();
+    void deprecatedDidCommitFrameLoad() { m_legacyCounter.updateMeasurements(); }
+
+    void recordMeasurement(Feature);
+    bool hasRecordedMeasurement(Feature feature) const { return m_featuresReported.quickGet(feature); }

[dtapuska, 2016/05/31 01:10:51]

The semantics of this are changing wrt muted count. 

 
     static UseCounter* getFrom(const Document*);
     static UseCounter* getFrom(const CSSStyleSheet*);
     static UseCounter* getFrom(const StyleSheetContents*);
 
-    static int mapCSSPropertyIdToCSSSampleIdForHistogram(int id);
+    static int mapCSSPropertyIdToCSSSampleIdForHistogram(CSSPropertyID);
 
     static void muteForInspector();
     static void unmuteForInspector();
-
-    void recordMeasurement(Feature feature) { m_countBits.recordMeasurement(feature); }
-    void updateMeasurements();
-
-    bool hasRecordedMeasurement(Feature feature) const { return m_countBits.hasRecordedMeasurement(feature); }
-
-    class CountBits {
-        DISALLOW_NEW();
-    public:
-        CountBits() : m_bits(NumberOfFeatures) { }
-
-        bool hasRecordedMeasurement(Feature feature) const
-        {
-            if (UseCounter::m_muteCount)
-                return false;
-            ASSERT(feature != PageDestruction); // PageDestruction is reserved as a scaling factor.
-            ASSERT(feature < NumberOfFeatures);
-
-            return m_bits.quickGet(feature);
-        }
-
-        void recordMeasurement(Feature feature)
-        {
-            if (UseCounter::m_muteCount)
-                return;
-            ASSERT(feature != PageDestruction); // PageDestruction is reserved as a scaling factor.
-            ASSERT(feature < NumberOfFeatures);
-
-            m_bits.quickSet(feature);
-        }
-
-        void updateMeasurements();
-
-    private:
-        BitVector m_bits;
-    };
+    static bool isMuted() { return m_muteCount; }
 
 protected:
+    BitVector m_featuresReported;
+    BitVector m_CSSFeaturesReported;
+
     friend class UseCounterTest;
     static int m_muteCount;
 
-    CountBits m_countBits;
-    BitVector m_CSSFeatureBits;
+private:
+    // Encapsulates the work to preserve the old "FeatureObserver" histogram with original (buggy)
+    // semantics.  Will be removed eventually.  http://crbug.com/597963
+    class LegacyCounter {
+    public:
+        LegacyCounter();
+        ~LegacyCounter();
+        void recordMeasurement(Feature);
+        void updateMeasurements();
+        bool hasRecordedMeasurement(Feature) const;

[dtapuska, 2016/05/31 01:10:51]

Is this method called anywhere?

+        void countCSS(CSSPropertyID feature);

[dtapuska, 2016/05/31 01:10:51]

Likely using a consistent verbage here is good. Count vs record. It is different
for features vs css. 

+
+    private:
+        BitVector m_countBits;
+        BitVector m_CSSFeatureBits;
+    } m_legacyCounter;
 };
 
 } // namespace blink
 
 #endif // UseCounter_h