Add touch drag UMA latency metric.

content/browser/renderer_host/input/input_router_client.h

Index: content/browser/renderer_host/input/input_router_client.h
diff --git a/content/browser/renderer_host/input/input_router_client.h b/content/browser/renderer_host/input/input_router_client.h
index 34fdf0eb9b7783bcbcaea9701dd46a4a71d079e9..b0fc5d3ee4d320bf606cdcccd38e9eaab98610a4 100644
--- a/content/browser/renderer_host/input/input_router_client.h
+++ b/content/browser/renderer_host/input/input_router_client.h
@@ -33,6 +33,11 @@ class CONTENT_EXPORT InputRouterClient {
       const blink::WebInputEvent& input_event,
       const ui::LatencyInfo& latency_info) = 0;
 
+  // Called just prior to the event being sent to the renderer.
+  virtual void OnForwardEventToRenderer(
+      const blink::WebInputEvent& input_event,
+      ui::LatencyInfo* latency_info) = 0;
+
   // Called each time a WebInputEvent IPC is sent.
   virtual void IncrementInFlightEventCount() = 0;