Add touch drag UMA latency metric.

ui/events/latency_info.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_EVENTS_LATENCY_INFO_H_
 #define UI_EVENTS_LATENCY_INFO_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 26 matching lines @@
   // ---------------------------NORMAL COMPONENT-------------------------------
   // The original timestamp of the touch event which converts to scroll update.
   INPUT_EVENT_LATENCY_SCROLL_UPDATE_ORIGINAL_COMPONENT,
   // The original timestamp of the touch event which converts to the *first*
   // scroll update in a scroll gesture sequence.
   INPUT_EVENT_LATENCY_FIRST_SCROLL_UPDATE_ORIGINAL_COMPONENT,
   // Original timestamp for input event (e.g. timestamp from kernel).
   INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT,
   // Timestamp when the UI event is created.
   INPUT_EVENT_LATENCY_UI_COMPONENT,
+  // Timestamp when the event reaches the RWH.
+  INPUT_EVENT_LATENCY_REACHED_RWH_COMPONENT,
   // This is special component indicating there is rendering scheduled for
   // the event associated with this LatencyInfo on main thread.
   INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_MAIN_COMPONENT,
   // This is special component indicating there is rendering scheduled for
   // the event associated with this LatencyInfo on impl thread.
   INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_IMPL_COMPONENT,
   // Timestamp when a scroll update is forwarded to the main thread.
   INPUT_EVENT_LATENCY_FORWARD_SCROLL_UPDATE_TO_MAIN_COMPONENT,
   // Timestamp when the event's ack is received by the RWH.
   INPUT_EVENT_LATENCY_ACK_RWH_COMPONENT,
@@ skipping 176 matching lines @@
   bool terminated_;
 
 #if !defined(OS_IOS)
   friend struct IPC::ParamTraits<ui::LatencyInfo>;
 #endif
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_LATENCY_INFO_H_