Add UMA/Telemetry stats for end-to-end scroll latency

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index 51dc59c8003fb25a1ad420963ba158e0e2df08d4..c851e45c2fdadc7d420ed39f9af05c424b54cab9 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -538,8 +538,11 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
       const WebKit::WebMouseWheelEvent& wheel_event,
       const ui::LatencyInfo& latency_info);
 
-  // Create a LatencyInfo struct for a new input event that was just received.
-  ui::LatencyInfo NewInputLatencyInfo();
+  // Create a LatencyInfo struct with INPUT_EVENT_LATENCY_RWH_COMPONENT
+  // component if it is not already in |original|. And if |original| is
+  // not NULL, it is also merged into the resulting LatencyInfo.
+  ui::LatencyInfo CreateRWHLatencyInfoIfNotExist(
+      const ui::LatencyInfo* original);
 
   // Called when we receive a notification indicating that the renderer
   // process has gone. This will reset our state so that our state will be