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..e38099152463288c83ad3b5ed0103eff8222edd0 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -2565,6 +2565,88 @@ void RenderWidgetHostImpl::DetachDelegate() {
   delegate_ = NULL;
 }
 
+void RenderWidgetHostImpl::ComputeTouchLatency(
+    const ui::LatencyInfo& latency_info) {
+  typedef ui::LatencyInfo::LatencyMap::const_iterator LatencyIter;
+  const ui::LatencyInfo::LatencyMap& latency_map =
+      latency_info.latency_components;
+
+  LatencyIter ui_it = latency_info.GetLatencyComponent(
+      ui::INPUT_EVENT_LATENCY_UI_COMPONENT, 0);
+
+  LatencyIter rwh_it = latency_info.GetLatencyComponent(
+      ui::INPUT_EVENT_LATENCY_RWH_COMPONENT,
+      GetLatencyComponentId());
+
+  if (rwh_it == latency_map.end() || ui_it == latency_map.end())
+    return;
+
+  DCHECK(ui_it->second.event_count == 1);
+  DCHECK(rwh_it->second.event_count == 1);
+
+  base::TimeDelta ui_delta =
+      rwh_it->second.event_time - ui_it->second.event_time;
+  rendering_stats_.touch_ui_count++;
+  rendering_stats_.total_touch_ui_latency += ui_delta;
+  UMA_HISTOGRAM_CUSTOM_COUNTS(
+      "Event.Latency.Touch.UI",
+      ui_delta.InMicroseconds(),
+      0,
+      20000,
+      100);
+
+  LatencyIter acked_consumed_it = latency_info.GetLatencyComponent(
+      ui::INPUT_EVENT_LATENCY_ACKED_COMPONENT,
+      INPUT_EVENT_ACK_STATE_CONSUMED);
+
+  LatencyIter acked_not_consumed_it = latency_info.GetLatencyComponent(
+      ui::INPUT_EVENT_LATENCY_ACKED_COMPONENT,
+      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+
+  LatencyIter acked_no_consumer_it = latency_info.GetLatencyComponent(
+      ui::INPUT_EVENT_LATENCY_ACKED_COMPONENT,
+      INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS);
+
+  if (acked_consumed_it != latency_map.end()) {
+    base::TimeDelta acked_delta =
+        acked_consumed_it->second.event_time - rwh_it->second.event_time;
+    rendering_stats_.touch_acked_consumed_count++;
+    rendering_stats_.total_touch_acked_consumed_latency += acked_delta;

[Rick Byers, 2013/06/26 21:42:10]

you could probably make this code more concise by flattening all 3 cases into
one with 3-element arrays in rendering_stats and an enum which chooses which
arrays to update and which string to use for the UMA metric.

[Yufeng Shen (Slow to review), 2013/06/26 23:02:26]

After a second thought, I find I don't have strong justification for having
stats for 3 different ack response and it unnecessarily complicated. So I
changed it to be just one metric just for acked touch event latency.

[Yufeng Shen (Slow to review), 2013/06/26 23:02:26]

After a second thought, I find I have no strong justification for
having stats for 3 different ack responses and it unnecessarily makes code
complicated. So I change to just use one metric for touch event ack latency.

+    UMA_HISTOGRAM_CUSTOM_COUNTS(
+        "Event.Latency.Touch.Acked_Consumed",
+        acked_delta.InMicroseconds(),
+        0,
+        100000,

[Rick Byers, 2013/06/26 21:42:10]

100ms might be too short, especially on Android.  Suggest using 1s as the upper
bound instead.

[Yufeng Shen (Slow to review), 2013/06/26 23:02:26]

Done.

+        100);
+  } else if (acked_not_consumed_it != latency_map.end()) {
+    base::TimeDelta acked_delta =
+        acked_not_consumed_it->second.event_time - rwh_it->second.event_time;
+    rendering_stats_.touch_acked_not_consumed_count++;
+    rendering_stats_.total_touch_acked_not_consumed_latency += acked_delta;
+    UMA_HISTOGRAM_CUSTOM_COUNTS(
+        "Event.Latency.Touch.Acked_Not_Consumed",
+        acked_delta.InMicroseconds(),
+        0,
+        100000,
+        100);
+  } else if (acked_no_consumer_it != latency_map.end()) {
+    base::TimeDelta acked_delta =
+        acked_no_consumer_it->second.event_time - rwh_it->second.event_time;
+    rendering_stats_.touch_acked_no_consumer_count++;
+    rendering_stats_.total_touch_acked_no_consumer_latency += acked_delta;
+    UMA_HISTOGRAM_CUSTOM_COUNTS(
+        "Event.Latency.Touch.Acked_No_Consumer_Exists",
+        acked_delta.InMicroseconds(),
+        0,
+        100000,
+        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(