Add UMA/Telemetry stats for touch event latency

content/browser/renderer_host/render_widget_host_impl.cc

Index: content/browser/renderer_host/render_widget_host_impl.cc
diff --git a/content/browser/renderer_host/render_widget_host_impl.cc b/content/browser/renderer_host/render_widget_host_impl.cc
index f37ec19ffa63c05d5d0d9437495f846648e3396b..bbd154f13a40952fa4fe7e1d8784d1a1876bbbd2 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -2565,6 +2565,53 @@ void RenderWidgetHostImpl::DetachDelegate() {
   delegate_ = NULL;
 }
 
+void RenderWidgetHostImpl::ComputeTouchLatency(
+    const ui::LatencyInfo& latency_info) {
+  ui::LatencyInfo::LatencyComponent ui_component;
+  ui::LatencyInfo::LatencyComponent rwh_component;
+  ui::LatencyInfo::LatencyComponent acked_component;
+
+  if (!latency_info.FindLatency(ui::INPUT_EVENT_LATENCY_UI_COMPONENT,
+                                0,
+                                &ui_component) ||
+      !latency_info.FindLatency(ui::INPUT_EVENT_LATENCY_RWH_COMPONENT,
+                                GetLatencyComponentId(),
+                                &rwh_component))
+    return;
+
+  DCHECK(ui_component.event_count == 1);
+  DCHECK(rwh_component.event_count == 1);
+
+  base::TimeDelta ui_delta =
+      rwh_component.event_time - ui_component.event_time;
+  rendering_stats_.touch_ui_count++;
+  rendering_stats_.total_touch_ui_latency += ui_delta;
+  UMA_HISTOGRAM_CUSTOM_COUNTS(
+      "Event.Latency.Browser.TouchUI",
+      ui_delta.InMicroseconds(),
+      0,
+      20000,
+      100);
+
+  latency_info.FindLatency(ui::INPUT_EVENT_LATENCY_ACKED_COMPONENT,

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

Check return value of FindLatency

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

Done.

+                           0,
+                           &acked_component);
+  base::TimeDelta acked_delta =
+      acked_component.event_time - rwh_component.event_time;
+  rendering_stats_.touch_acked_count++;
+  rendering_stats_.total_touch_acked_latency += acked_delta;
+  UMA_HISTOGRAM_CUSTOM_COUNTS(
+      "Event.Latency.Browser.TouchAcked",
+      acked_delta.InMicroseconds(),
+      0,
+      1000000,
+      100);
+
+  if (CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableGpuBenchmarking))
+    Send(new ViewMsg_SetBrowserRenderingStats(routing_id_, rendering_stats_));
+}
+
 void RenderWidgetHostImpl::FrameSwapped(const ui::LatencyInfo& latency_info) {
   ui::LatencyInfo::LatencyMap::const_iterator l =
       latency_info.latency_components.find(std::make_pair(