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

content/common/browser_rendering_stats.cc

Index: content/common/browser_rendering_stats.cc
diff --git a/content/common/browser_rendering_stats.cc b/content/common/browser_rendering_stats.cc
index 9c0c8259de5e53c262bd66dc27b0244d511de2ba..6fe309048479964b1b61de534910ddc6644e3a0f 100644
--- a/content/common/browser_rendering_stats.cc
+++ b/content/common/browser_rendering_stats.cc
@@ -10,7 +10,9 @@ BrowserRenderingStats::BrowserRenderingStats() :
     input_event_count(0),
     touch_ui_count(0),
     touch_acked_count(0),
-    scroll_update_count(0) {
+    scroll_update_count(0),
+    impl_to_main_touch_event_count(0),
+    impl_to_main_gesture_scroll_event_count(0) {
 }
 
 BrowserRenderingStats::~BrowserRenderingStats() {}
@@ -31,6 +33,15 @@ void BrowserRenderingStats::EnumerateFields(
   enumerator->AddInt("scrollUpdateCount", scroll_update_count);
   enumerator->AddTimeDeltaInSecondsF("totalScrollUpdateLatency",
                                      total_scroll_update_latency);
+
+  enumerator->AddInt("implToMainTouchEventCount",
+                       impl_to_main_touch_event_count);
+  enumerator->AddTimeDeltaInSecondsF("totalImplToMainTouchEventLatency",
+                                     total_impl_to_main_touch_event_latency);
+  enumerator->AddInt("implToMainGestureScrollEventCount",
+                       impl_to_main_gesture_scroll_event_count);
+  enumerator->AddTimeDeltaInSecondsF("totalImplToMainGestureScrollEventLatency",
+      total_impl_to_main_gesture_scroll_event_latency);
 }
 
 }  // namespace content