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 c5933f563bf89a604d9bee463d9c0cf02683d54d..bf95bfabdd7f072640534e54554b6856e9a6ec67 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -537,8 +537,10 @@ 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 |original| is not NULL, it is merged into the resulting
+  // LatencyInfo.
+  ui::LatencyInfo NewInputLatencyInfo(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