Report LatencyInfo through trace buffer

content/browser/renderer_host/input/touch_event_queue.cc

 // 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.
 
 #include "content/browser/renderer_host/input/touch_event_queue.h"
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "base/stl_util.h"
 
@@ skipping 176 matching lines @@
     const ui::LatencyInfo& renderer_latency_info) {
   if (touch_queue_.empty())
     return;
   scoped_ptr<CoalescedWebTouchEvent> acked_event(touch_queue_.front());
   touch_queue_.pop_front();
 
   // Note that acking the touch-event may result in multiple gestures being sent
   // to the renderer, or touch-events being queued.
   base::AutoReset<bool> dispatching_touch_ack(&dispatching_touch_ack_, true);
 
-  base::TimeTicks now = base::TimeTicks::HighResNow();
   for (WebTouchEventWithLatencyList::const_iterator iter = acked_event->begin(),
        end = acked_event->end();
        iter != end; ++iter) {
     ui::LatencyInfo* latency = const_cast<ui::LatencyInfo*>(&(iter->latency));

[jdduke (slow), 2013/10/01 23:45:31]

Sorry, this isn't directly related to your patch, but this const_cast kills me,
could you go ahead and just make this a regular iterator?  You can change
CoalescedWebTouchEvent to return an iterator(), I believe this is the only place
we use it.

Bonus points for getting rid of begin()/end() calls entirely, and adding a
CoalescedWebTouchEvent::DispatchAckTo(client, renderer_latency_info, ack_result)
that does the dispatch there =/

[Yufeng Shen (Slow to review), 2013/10/04 00:29:51]

Done.

     latency->AddNewLatencyFrom(renderer_latency_info);
-    latency->AddLatencyNumberWithTimestamp(
-        ui::INPUT_EVENT_LATENCY_ACKED_COMPONENT, 0, 0, now, 1);
     client_->OnTouchEventAck((*iter), ack_result);
   }
 }
 
 bool TouchEventQueue::ShouldForwardToRenderer(
     const WebKit::WebTouchEvent& event) const {
   // Touch press events should always be forwarded to the renderer.
   if (event.type == WebKit::WebInputEvent::TouchStart)
     return true;
 
@@ skipping 15 matching lines @@
       // If the ACK status of a point is unknown, then the event should be
       // forwarded to the renderer.
       return true;
     }
   }
 
   return false;
 }
 
 }  // namespace content