Adding UseCounter specific for extensions

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 49 matching lines @@
 //
 // Changes on UseCounter are observable by UseCounter::Observer.
 class CORE_EXPORT UseCounter {
   DISALLOW_NEW();
   WTF_MAKE_NONCOPYABLE(UseCounter);
 
  public:
   enum Context {
     kDefaultContext,
     // Counters for SVGImages (lifetime independent from other pages).
-    kSVGImageContext
+    kSVGImageContext,
+    // Counters for extensions.
+    kExtensionContext,
+    // Context when counters should be disabled (eg, internal pages such as
+    // about, chrome-devtools, etc).
+    kDisabledContext
   };
 
   UseCounter(Context = kDefaultContext);
 
   enum Feature : uint32_t {
     // Do not change assigned numbers of existing items: add new features
     // to the end of the list.
     kOBSOLETE_PageDestruction = 0,
     kWorkerStart = 4,
     kSharedWorkerStart = 5,
@@ skipping 1499 matching lines @@
     kGamepadButtons = 1965,
 
     // 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.
     kNumberOfFeatures,  // 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|.
+  // notified when the counter is disabled by |m_muteCount| or when |m_context|
+  // is DisabledContext.
   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() {}
   };
 
@@ skipping 41 matching lines @@
 
   // 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|.
+  // be called when the counter is disabled by |m_muteCount| or when |m_context|
+  // if DisabledContext.
   void NotifyFeatureCounted(Feature);
 
   EnumerationHistogram& FeaturesHistogram() const;
   EnumerationHistogram& CssHistogram() const;
   EnumerationHistogram& AnimatedCSSHistogram() const;
 
   // If non-zero, ignore all 'count' calls completely.
   unsigned mute_count_;
 
-  // If true, disable reporting all histogram entries.
-  bool disable_reporting_;
-
   // The scope represented by this UseCounter instance.

[Rick Byers, 2017/04/28 15:04:40]

Nit: can you add a comment saying that this must be fixed for the duration of a
page, but can change when a new page is loaded.
"by this instance" want originally meant to imply it was fixed (I should have
used const to make that clear of course).

[lunalu1, 2017/05/01 15:37:52]

Done. Thanks

   Context context_;
 
   // Track what features/properties have been reported to the (non-legacy)
   // histograms.
   BitVector features_recorded_;
   BitVector css_recorded_;
   BitVector animated_css_recorded_;
 
   HeapHashSet<Member<Observer>> observers_;
 
@@ skipping 12 matching lines @@
     // Tracks what features/properties need to be reported to the legacy
     // histograms.
     BitVector feature_bits_;
     BitVector css_bits_;
   } legacy_counter_;
 };
 
 }  // namespace blink
 
 #endif  // UseCounter_h