Add telemetry to track the time an event spent waiting for the main thread.

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 edd21fe5987575faff070ae5dc9e50fd355d00f0..30ec7961820af78dbf831ef02897370e739eed09 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -2100,14 +2100,16 @@ void RenderWidgetHostImpl::OnWheelEventAck(
 }
 
 void RenderWidgetHostImpl::OnGestureEventAck(
-    const WebKit::WebGestureEvent& event,
+    const GestureEventWithLatencyInfo& event,
     InputEventAckState ack_result) {
   const bool processed = (INPUT_EVENT_ACK_STATE_CONSUMED == ack_result);
   if (overscroll_controller_)
-    overscroll_controller_->ReceivedEventACK(event, processed);
+    overscroll_controller_->ReceivedEventACK(event.event, processed);
 
   if (view_)
-    view_->GestureEventAck(event.type, ack_result);
+    view_->GestureEventAck(event.event.type, ack_result);
+
+  UpdateRenderingStatsForImplThreadLatency(event.event.type, event.latency);
 }
 
 void RenderWidgetHostImpl::OnTouchEventAck(
@@ -2364,6 +2366,39 @@ void RenderWidgetHostImpl::DelayedAutoResized() {
   OnRenderAutoResized(new_size);
 }
 
+void RenderWidgetHostImpl::UpdateRenderingStatsForImplThreadLatency(

[nduca, 2013/08/15 01:41:04]

I'd like to see you modify enough of the input router etc so that InputRouter is
able to track stats. E.g. every input event that you give to the input router
comes back with latency info. Can you think of a way to change the host side
interfaces to permit this?

+    WebKit::WebInputEvent::Type type,
+    const ui::LatencyInfo& latency_info) {
+  ui::LatencyInfo::LatencyComponent dispatch_component;
+  ui::LatencyInfo::LatencyComponent receive_component;
+  if (!latency_info.FindLatency(
+          ui::INPUT_EVENT_LATENCY_EVENT_SENT_FROM_IMPL_THREAD_COMPONENT,
+          routing_id_, &dispatch_component) ||
+      !latency_info.FindLatency(
+          ui::INPUT_EVENT_LATENCY_EVENT_RECEIVED_ON_MAIN_THREAD_COMPONENT,
+          routing_id_, &receive_component))
+    return;
+
+  bool stats_changed = false;
+  if (WebKit::WebInputEvent::isTouchEventType(type)) {
+    rendering_stats_.total_impl_to_main_touch_event_latency +=
+        (receive_component.event_time - dispatch_component.event_time);
+    rendering_stats_.impl_to_main_touch_event_count++;
+    stats_changed = true;
+  } else if (type == WebKit::WebInputEvent::GestureScrollBegin ||
+      type == WebKit::WebInputEvent::GestureScrollUpdate ||
+      type == WebKit::WebInputEvent::GestureScrollUpdateWithoutPropagation) {
+    rendering_stats_.total_impl_to_main_gesture_scroll_event_latency +=
+        (receive_component.event_time - dispatch_component.event_time);
+    rendering_stats_.impl_to_main_gesture_scroll_event_count++;
+    stats_changed = true;
+  }
+
+  if (stats_changed && CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableGpuBenchmarking))
+    Send(new ViewMsg_SetBrowserRenderingStats(routing_id_, rendering_stats_));
+}
+
 void RenderWidgetHostImpl::DetachDelegate() {
   delegate_ = NULL;
 }