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 7d4b70c5aa0d20625061b4ab508d424632e8a488..a7cedcbc3ddb9826958be04b6a76c4e655884a4d 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -737,6 +737,31 @@ void LayerTreeHost::ApplyViewportDeltas(ScrollAndScaleSet* info) {
   SetNeedsUpdateLayers();
 }
 
+void LayerTreeHost::RecordWheelAndTouchScrollingCount(ScrollAndScaleSet* info) {
+  bool has_scrolled_by_wheel = false;
+  bool has_scrolled_by_touch = false;
+
+  if (!info)
+    return;
+
+  switch (info->scroll_source_info) {
+    case InputHandler::ScrollSourceInfo::NONE:
+      break;

[dtapuska, 2017/03/08 21:18:00]

Can you return here?

[sahel, 2017/03/10 16:21:33]

Done.

+    case InputHandler::ScrollSourceInfo::SCROLLED_BY_TOUCH:
+      has_scrolled_by_touch = true;
+      break;
+    case InputHandler::ScrollSourceInfo::SCROLLED_BY_WHEEL:
+      has_scrolled_by_wheel = true;
+      break;
+    case InputHandler::ScrollSourceInfo::SCROLLED_BY_TOUCH_AND_WHEEL:
+      has_scrolled_by_wheel = true;
+      has_scrolled_by_touch = true;
+      break;
+  }
+  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",
@@ -767,6 +792,8 @@ 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()