Add UMA metric for tracking listeners for blocking touch while fling is happening

content/renderer/input/input_event_filter.cc

Index: content/renderer/input/input_event_filter.cc
diff --git a/content/renderer/input/input_event_filter.cc b/content/renderer/input/input_event_filter.cc
index e62ee2cf941c784c96db901db93940ae26ccb648..e83071291434e3c2ef4286020d9da6e92ca69741 100644
--- a/content/renderer/input/input_event_filter.cc
+++ b/content/renderer/input/input_event_filter.cc
@@ -50,7 +50,9 @@ InputEventFilter::InputEventFilter(
       main_listener_(main_listener),
       sender_(NULL),
       target_task_runner_(target_task_runner),
-      current_overscroll_params_(NULL) {
+      current_overscroll_params_(NULL),
+      is_flinging_on_main_(false),
+      is_flinging_on_impl_(false) {
   DCHECK(target_task_runner_.get());
 }
 
@@ -83,9 +85,18 @@ void InputEventFilter::DidOverscroll(int routing_id,
 }
 
 void InputEventFilter::DidStopFlinging(int routing_id) {
+  is_flinging_on_main_ = false;
+  is_flinging_on_impl_ = false;
   SendMessage(base::WrapUnique(new InputHostMsg_DidStopFlinging(routing_id)));
 }
 
+void InputEventFilter::DidStartFlinging(bool is_on_impl) {
+  if (is_on_impl)
+    is_flinging_on_impl_ = true;
+  else
+    is_flinging_on_main_ = true;
+}
+
 void InputEventFilter::NotifyInputEventHandled(
     int routing_id,
     blink::WebInputEvent::Type type) {
@@ -183,8 +194,9 @@ void InputEventFilter::ForwardToHandler(const IPC::Message& message) {
     DCHECK(!overscroll_params);
     RouteQueueMap::iterator iter = route_queues_.find(routing_id);
     if (iter != route_queues_.end())
-      send_ack &= iter->second->HandleEvent(event, latency_info, dispatch_type,
-                                            ack_state);
+      send_ack &= iter->second->HandleEvent(
+          event, latency_info, dispatch_type, ack_state,
+          (is_flinging_on_main_ || is_flinging_on_impl_));
   }
 
   if (!send_ack)