UMA metrics for use count of wheel and touch scrolls.

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 3cb2718837c23b44c9f87eee2194f13418c749f8..fd455dd95b29449e5d238a167e9af1c25421e1c5 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -756,6 +756,16 @@ void LayerTreeHost::ApplyViewportDeltas(ScrollAndScaleSet* info) {
   SetNeedsUpdateLayers();
 }
 
+void LayerTreeHost::RecordWheelAndTouchScrollingCount(ScrollAndScaleSet* info) {
+  bool has_scrolled_by_wheel = info->has_scrolled_by_wheel;
+  bool has_scrolled_by_touch = info->has_scrolled_by_touch;
+
+  if (has_scrolled_by_wheel || has_scrolled_by_touch) {
+    client_->RecordWheelAndTouchScrollingCount(has_scrolled_by_wheel,
+                                               has_scrolled_by_touch);
+  }
+}
+
 void LayerTreeHost::ApplyScrollAndScale(ScrollAndScaleSet* info) {
   for (auto& swap_promise : info->swap_promises) {
     TRACE_EVENT_WITH_FLOW1("input,benchmark", "LatencyInfo.Flow",
@@ -786,6 +796,8 @@ void LayerTreeHost::ApplyScrollAndScale(ScrollAndScaleSet* info) {
   // controls from clamping the layout viewport both on the compositor and
   // on the main thread.
   ApplyViewportDeltas(info);
+
+  RecordWheelAndTouchScrollingCount(info);
 }
 
 const base::WeakPtr<InputHandler>& LayerTreeHost::GetInputHandler()