Don't use PostTask queueing between compositor and main thread.

content/common/input/input_event_dispatch_type.h

 // Copyright 2016 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.
 
 #ifndef CONTENT_COMMON_INPUT_INPUT_EVENT_DISPATCH_TYPE_H_
 #define CONTENT_COMMON_INPUT_INPUT_EVENT_DISPATCH_TYPE_H_
 
 namespace content {
 
 enum InputEventDispatchType {
   // Dispatch a blocking event. Sender is waiting on an ACK.
   DISPATCH_TYPE_BLOCKING,
   // Dispatch a blocking event and notify main thread as well. This type
   // should only be sent from the compositor to main thread.
   DISPATCH_TYPE_BLOCKING_NOTIFY_MAIN,
   // Dispatch a non-blocking event. Sender will not receive an ACK.
   DISPATCH_TYPE_NON_BLOCKING,
-  // Dispatch a non-blocking event and notify main thread as well. This type
-  // should only be sent from the compositor to main thread.
-  DISPATCH_TYPE_NON_BLOCKING_NOTIFY_MAIN,
-  DISPATCH_TYPE_MAX = DISPATCH_TYPE_NON_BLOCKING_NOTIFY_MAIN
+  DISPATCH_TYPE_MAX = DISPATCH_TYPE_NON_BLOCKING
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_INPUT_INPUT_EVENT_DISPATCH_TYPE_H_