Add UMA/Telemetry stats for touch event latency

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index 78db0cbfb3cea2e2aed3ed7744dd7dcbfd0cec2f..f63c7ba653364fbc9eb3ef6b6844bdbe34bb6d44 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -1802,9 +1802,8 @@ void RenderWidgetHostViewAura::ProcessAckedTouchEvent(
   for (ScopedVector<ui::TouchEvent>::iterator iter = events.begin(),
       end = events.end(); iter != end; ++iter) {
     (*iter)->latency()->AddLatencyNumber(
-        ui::INPUT_EVENT_LATENCY_ACKED_COMPONENT,
-        static_cast<int64>(ack_result),
-        0);
+        ui::INPUT_EVENT_LATENCY_ACKED_COMPONENT, 0, 0);
+    host_->ComputeTouchLatency(*((*iter)->latency()));

[sadrul, 2013/06/27 17:44:01]

Why is this called from here? Why not from
RWHI::OnInputEventAck/ProcessTouchAck?

[Yufeng Shen (Slow to review), 2013/06/27 19:01:03]

right, it is better to be in RWHI or touch_event_queue so we don't need to
do this for each view port.

Since we want to add the ACKED_COMPONENT for each uncoalesced (Web/UI)touch
event so I feel it is proper to do it in TouchEventQueue::PopTouchEventToView()
where we extract each individual touch event out and before calling view's
ProcessAckedTouchEvent.
So move the code to TouchEventQueue::PopTouchEventToView(). 

     root->ProcessedTouchEvent((*iter), window_, result);
   }
 }