Adding UseCounter specific for extensions

third_party/WebKit/Source/core/frame/UseCounter.cpp

Index: third_party/WebKit/Source/core/frame/UseCounter.cpp
diff --git a/third_party/WebKit/Source/core/frame/UseCounter.cpp b/third_party/WebKit/Source/core/frame/UseCounter.cpp
index 6c363695c2ef34a4f9d0a9ca6274b69d8ad3ca28..cb928475a0ac592967234e6e01324f769902c97c 100644
--- a/third_party/WebKit/Source/core/frame/UseCounter.cpp
+++ b/third_party/WebKit/Source/core/frame/UseCounter.cpp
@@ -1175,7 +1175,10 @@ void UseCounter::didCommitLoad(KURL url) {
   m_CSSRecorded.clearAll();
   m_animatedCSSRecorded.clearAll();
   if (!m_disableReporting && !m_muteCount) {
-    featuresHistogram().count(PageVisits);
+    if (url.protocolIs("chrome-extension"))

[Rick Byers, 2017/04/07 17:46:54]

I think m_disableReporting will still be true in this case, right?

+      extensionFeaturesHistogram().count(PageVisits);
+    else
+      featuresHistogram().count(PageVisits);
     cssHistogram().count(totalPagesMeasuredCSSSampleId());
     animatedCSSHistogram().count(totalPagesMeasuredCSSSampleId());
   }
@@ -1334,6 +1337,13 @@ EnumerationHistogram& UseCounter::featuresHistogram() const {
   return m_context == SVGImageContext ? svgHistogram : histogram;
 }
 
+EnumerationHistogram& UseCounter::extensionFeaturesHistogram() const {
+  DEFINE_STATIC_LOCAL(blink::EnumerationHistogram, histogram,
+                      ("Blink.UseCounter.Extensions.Features",
+                       blink::UseCounter::NumberOfFeatures));
+  return histogram;
+}
+
 EnumerationHistogram& UseCounter::cssHistogram() const {
   DEFINE_STATIC_LOCAL(blink::EnumerationHistogram, histogram,
                       ("Blink.UseCounter.CSSProperties", kMaximumCSSSampleId));