Add touch drag UMA latency metric.

content/browser/renderer_host/input/input_router_impl.h

Index: content/browser/renderer_host/input/input_router_impl.h
diff --git a/content/browser/renderer_host/input/input_router_impl.h b/content/browser/renderer_host/input/input_router_impl.h
index 9315f6fa379dec63888c64718f12854f5c018b83..8e76015f52ad62296279fd980acb2f0f1357d796 100644
--- a/content/browser/renderer_host/input/input_router_impl.h
+++ b/content/browser/renderer_host/input/input_router_impl.h
@@ -113,13 +113,13 @@ class CONTENT_EXPORT InputRouterImpl
 
   // Filters and forwards |input_event| to the appropriate handler.
   void FilterAndSendWebInputEvent(const blink::WebInputEvent& input_event,
-                                  const ui::LatencyInfo& latency_info);
+                                  ui::LatencyInfo* latency_info);
 
   // Utility routine for filtering and forwarding |input_event| to the
   // appropriate handler. |input_event| will be offered to the overscroll
   // controller, client and renderer, in that order.
   void OfferToHandlers(const blink::WebInputEvent& input_event,
-                       const ui::LatencyInfo& latency_info);
+                       ui::LatencyInfo* latency_info);
 
   // Returns true if |input_event| was consumed by the client.
   bool OfferToClient(const blink::WebInputEvent& input_event,
@@ -128,8 +128,8 @@ class CONTENT_EXPORT InputRouterImpl
   // Returns true if |input_event| was successfully sent to the renderer
   // as an async IPC Message.
   bool OfferToRenderer(const blink::WebInputEvent& input_event,
-                       const ui::LatencyInfo& latency_info,
-                       InputEventDispatchType dispatch_type);
+                       InputEventDispatchType dispatch_type,
+                       ui::LatencyInfo* latency_info);
 
   // IPC message handlers
   void OnInputEventAck(const InputEventAck& ack);