Force events to be non blocking if main thread is unresponsive.

content/renderer/input/render_widget_input_handler.cc

Index: content/renderer/input/render_widget_input_handler.cc
diff --git a/content/renderer/input/render_widget_input_handler.cc b/content/renderer/input/render_widget_input_handler.cc
index 46bd4c5250fdff995699cbae0748896bf002d9d5..84249ba7d98e25b24fba312c9cf5ee200cf5e7e1 100644
--- a/content/renderer/input/render_widget_input_handler.cc
+++ b/content/renderer/input/render_widget_input_handler.cc
@@ -124,6 +124,7 @@ void LogPassiveEventListenersUma(WebInputEventResult result,
     PASSIVE_LISTENER_UMA_ENUM_CANCELABLE,
     PASSIVE_LISTENER_UMA_ENUM_CANCELABLE_AND_CANCELED,
     PASSIVE_LISTENER_UMA_ENUM_FORCED_NON_BLOCKING_DUE_TO_FLING,
+    PASSIVE_LISTENER_UMA_ENUM_FORCED_NON_BLOCKING_DUE_TO_MAIN_THREAD_RESPONSIVENESS,
     PASSIVE_LISTENER_UMA_ENUM_COUNT
   };
 
@@ -132,6 +133,10 @@ void LogPassiveEventListenersUma(WebInputEventResult result,
     case WebInputEvent::ListenersForcedNonBlockingDueToFling:
       enum_value = PASSIVE_LISTENER_UMA_ENUM_FORCED_NON_BLOCKING_DUE_TO_FLING;
       break;
+    case WebInputEvent::ListenersForcedNonBlockingDueToMainThreadResponsiveness:
+      enum_value =
+          PASSIVE_LISTENER_UMA_ENUM_FORCED_NON_BLOCKING_DUE_TO_MAIN_THREAD_RESPONSIVENESS;
+      break;
     case WebInputEvent::ListenersNonBlockingPassive:
       enum_value = PASSIVE_LISTENER_UMA_ENUM_PASSIVE;
       break;
@@ -166,6 +171,14 @@ void LogPassiveEventListenersUma(WebInputEventResult result,
       UMA_HISTOGRAM_CUSTOM_COUNTS(
           "Event.PassiveListeners.ForcedNonBlockingLatencyDueToFling",
           GetEventLatencyMicros(event_timestamp, now), 1, 10000000, 100);
+    } else if (
+        enum_value ==
+        PASSIVE_LISTENER_UMA_ENUM_FORCED_NON_BLOCKING_DUE_TO_MAIN_THREAD_RESPONSIVENESS) {
+      base::TimeTicks now = base::TimeTicks::Now();
+      UMA_HISTOGRAM_CUSTOM_COUNTS(
+          "Event.PassiveListeners."
+          "ForcedNonBlockingLatencyDueToUnresponsiveMainThread",
+          GetEventLatencyMicros(event_timestamp, now), 1, 10000000, 100);

[Ilya Sherman, 2016/12/16 00:46:02]

How valuable is it to have 100 buckets for these histograms?  In general, we
encourage histograms of 50 buckets or fewer, to reduce the costs of recording
such metrics.

[tdresser, 2016/12/16 13:32:43]

Reduced to 50 buckets. At some point I'll need to go through here and rename a
bunch of things and give them fewer buckets...

Thanks for catching this.

     }
   }
 }