Add UseCounter for HTML Imports

BUG=383749
TEST=none
R=dglazkov@chromium.org, hayato@chromium.org

Review URL: https://codereview.chromium.org/330543007

git-svn-id: svn://svn.chromium.org/blink/trunk@176041 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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

@@ -452,6 +452,7 @@ public:
         WebkitEditableContentChangedOnTextArea = 452,
         WebkitEditableContentChangedOnContentEditable = 453,
         WebkitEditableContentChangedOnNotNode = 454,
+        HTMLImports = 455,
         // 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/

third_party/WebKit/Source/core/html/imports/HTMLImportsController.cpp

@@ -34,6 +34,7 @@
 #include "core/dom/Document.h"
 #include "core/fetch/ResourceFetcher.h"
 #include "core/frame/LocalFrame.h"
+#include "core/frame/UseCounter.h"
 #include "core/html/imports/HTMLImportChild.h"
 #include "core/html/imports/HTMLImportChildClient.h"
 #include "core/html/imports/HTMLImportLoader.h"
@@ -52,6 +53,7 @@ void HTMLImportsController::provideTo(Document& master)
 HTMLImportsController::HTMLImportsController(Document& master)
     : m_root(HTMLImportTreeRoot::create(&master))
 {
+    UseCounter::count(master, UseCounter::HTMLImports);
 }
 
 HTMLImportsController::~HTMLImportsController()