Send input event IPCs directly from the UI thread

ipc/ipc_sync_channel.h

 // Copyright (c) 2012 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 IPC_IPC_SYNC_CHANNEL_H_
 #define IPC_IPC_SYNC_CHANNEL_H_
 
 #include <deque>
 #include <memory>
 #include <string>
@@ skipping 211 matching lines @@
 
   // Runs a nested message loop until a reply arrives, times out, or the process
   // shuts down.
   static void WaitForReplyWithNestedMessageLoop(SyncContext* context);
 
   // Starts the dispatch watcher.
   void StartWatching();
 
   // ChannelProxy overrides:
   void OnChannelInit() override;
+  bool SendNow(std::unique_ptr<Message> message) override;
+  bool SendOnIPCThread(std::unique_ptr<Message> message) override;
 
   // Used to signal events between the IPC and listener threads.
   base::WaitableEventWatcher dispatch_watcher_;
   base::WaitableEventWatcher::EventCallback dispatch_watcher_callback_;
 
   // Tracks SyncMessageFilters created before complete channel initialization.
   std::vector<scoped_refptr<SyncMessageFilter>> pre_init_sync_message_filters_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncChannel);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_SYNC_CHANNEL_H_