Adding UseCounter specific for extensions

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 c82c64a7577040b2cc60bec9595ad815bff122b6..aa78a114195be380fc07e14140c69304dd899c38 100644
--- a/third_party/WebKit/Source/core/frame/UseCounter.h
+++ b/third_party/WebKit/Source/core/frame/UseCounter.h
@@ -67,7 +67,12 @@ class CORE_EXPORT UseCounter {
   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);
@@ -1587,8 +1592,8 @@ class CORE_EXPORT UseCounter {
   };
 
   // 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
@@ -1650,8 +1655,8 @@ class CORE_EXPORT UseCounter {
 
  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;
@@ -1661,9 +1666,6 @@ class CORE_EXPORT UseCounter {
   // 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_;