UMA metrics for use count of wheel and touch scrolls.

cc/trees/layer_tree_host_client.h

Index: cc/trees/layer_tree_host_client.h
diff --git a/cc/trees/layer_tree_host_client.h b/cc/trees/layer_tree_host_client.h
index c0fcb4bef14dc0360864554c93a903668534cd07..03c2431f87476bcb135709d2745313b6e735d33d 100644
--- a/cc/trees/layer_tree_host_client.h
+++ b/cc/trees/layer_tree_host_client.h
@@ -43,6 +43,9 @@ class LayerTreeHostClient {
       const gfx::Vector2dF& elastic_overscroll_delta,
       float page_scale,
       float top_controls_delta) = 0;
+  virtual void RecordWheelAndTouchScrollingCount(
+      bool has_scrolled_by_wheel,
+      bool has_scrolled_by_touch) = 0;
   // Request an CompositorFrameSink from the client. When the client has one it
   // should call LayerTreeHost::SetCompositorFrameSink.  This will result in
   // either DidFailToInitializeCompositorFrameSink or