Add UMA stats for pinch-zoom behavior on Android

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

Index: third_party/WebKit/Source/core/frame/VisualViewport.h
diff --git a/third_party/WebKit/Source/core/frame/VisualViewport.h b/third_party/WebKit/Source/core/frame/VisualViewport.h
index e95eae3853d82bd45e1a2ba7c1fe5fea14aa65a4..fad61abcb0f71133f4541808611b3413960bf7da 100644
--- a/third_party/WebKit/Source/core/frame/VisualViewport.h
+++ b/third_party/WebKit/Source/core/frame/VisualViewport.h
@@ -195,6 +195,11 @@ public:
     GraphicsLayer* layerForHorizontalScrollbar() const override;
     GraphicsLayer* layerForVerticalScrollbar() const override;
 
+    // Used for gathering data on user pinch-zoom statistics.
+    void userDidChangeScale();
+    void sendUMAMetrics();
+    void startTrackingPinchStats();
+
 private:
     explicit VisualViewport(FrameHost&);
 
@@ -231,6 +236,8 @@ private:
     float m_scale;
     IntSize m_size;
     float m_topControlsAdjustment;
+    float m_maxPageScale;
+    bool m_trackPinchZoomStatsForPage;
 };
 
 } // namespace blink