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

content/renderer/input/render_widget_input_handler.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/input/render_widget_input_handler.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <utility>
 
@@ skipping 106 matching lines @@
                                  WebInputEvent::DispatchType dispatch_type,
                                  double event_timestamp,
                                  const ui::LatencyInfo& latency_info) {
   enum {
     PASSIVE_LISTENER_UMA_ENUM_PASSIVE,
     PASSIVE_LISTENER_UMA_ENUM_UNCANCELABLE,
     PASSIVE_LISTENER_UMA_ENUM_SUPPRESSED,
     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
   };
 
   int enum_value;
   switch (dispatch_type) {
     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;
     case WebInputEvent::EventNonBlocking:
       enum_value = PASSIVE_LISTENER_UMA_ENUM_UNCANCELABLE;
       break;
     case WebInputEvent::Blocking:
       if (result == WebInputEventResult::HandledApplication)
         enum_value = PASSIVE_LISTENER_UMA_ENUM_CANCELABLE_AND_CANCELED;
       else if (result == WebInputEventResult::HandledSuppressed)
@@ skipping 14 matching lines @@
       base::TimeTicks now = base::TimeTicks::Now();
       UMA_HISTOGRAM_CUSTOM_COUNTS("Event.PassiveListeners.Latency",
                                   GetEventLatencyMicros(event_timestamp, now),
                                   1, 10000000, 100);
     } else if (enum_value ==
                PASSIVE_LISTENER_UMA_ENUM_FORCED_NON_BLOCKING_DUE_TO_FLING) {
       base::TimeTicks now = base::TimeTicks::Now();
       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.

     }
   }
 }
 
 }  // namespace
 
 RenderWidgetInputHandler::RenderWidgetInputHandler(
     RenderWidgetInputHandlerDelegate* delegate,
     RenderWidget* widget)
     : delegate_(delegate),
@@ skipping 266 matching lines @@
   // it can be bundled in the event ack.
   if (handling_event_overscroll_) {
     *handling_event_overscroll_ = std::move(params);
     return;
   }
 
   delegate_->OnDidOverscroll(*params);
 }
 
 }  // namespace content