Move webfont usage metrics reporting to FontResource

Source/core/fetch/FontResource.h

Index: Source/core/fetch/FontResource.h
diff --git a/Source/core/fetch/FontResource.h b/Source/core/fetch/FontResource.h
index 42b4f7029d5e251de71241c5653d91dc3a384439..a910f8efaa91ce095a77d020e1139ea7cb2035f0 100644
--- a/Source/core/fetch/FontResource.h
+++ b/Source/core/fetch/FontResource.h
@@ -50,6 +50,7 @@ public:
     virtual void didAddClient(ResourceClient*);
 
     virtual void allClientsRemoved();
+    void willUseFontData();
     void beginLoadIfNeeded(ResourceFetcher* dl);
     bool stillNeedsLoad() const { return !m_loadInitiated; }
 
@@ -69,6 +70,22 @@ private:
 #if ENABLE(SVG_FONTS)
     RefPtr<WebCore::SVGDocument> m_externalSVGDocument;
 #endif
+    class FontResourceHistograms {
+    public:
+        enum UsageType {
+            StyledAndUsed,
+            StyledButNotUsed,
+            NotStyledButUsed,
+            UsageTypeMax
+        };
+        FontResourceHistograms() : m_styledTime(0) { }
+        ~FontResourceHistograms();
+        void willUseFontData();
+        void loadStarted();
+    private:
+        double m_styledTime;
+    };
+    FontResourceHistograms m_histograms;
 
     friend class MemoryCache;
 };