Send input event IPCs directly from the UI thread

ipc/ipc_sync_message_filter.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_MESSAGE_FILTER_H_
 #define IPC_IPC_SYNC_MESSAGE_FILTER_H_
 
+#include <memory>
 #include <set>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_vector.h"
 #include "base/synchronization/lock.h"
 #include "ipc/ipc_sender.h"
 #include "ipc/ipc_sync_message.h"
 #include "ipc/message_filter.h"
 
@@ skipping 14 matching lines @@
  public:
   // MessageSender implementation.
   bool Send(Message* message) override;
 
   // MessageFilter implementation.
   void OnFilterAdded(Sender* sender) override;
   void OnChannelError() override;
   void OnChannelClosing() override;
   bool OnMessageReceived(const Message& message) override;
 
+  // Like Send but may send immediately (instead of posting to the IPC thread)
+  // if the underlying Channel implements a thread-safe Send.
+  bool SendNow(std::unique_ptr<Message> message);
+
  protected:
   SyncMessageFilter(base::WaitableEvent* shutdown_event,
                     bool is_channel_send_thread_safe);
 
   ~SyncMessageFilter() override;
 
  private:
   friend class SyncChannel;
 
   void set_is_channel_send_thread_safe(bool is_channel_send_thread_safe) {
@@ skipping 26 matching lines @@
   base::Lock lock_;
 
   base::WaitableEvent* shutdown_event_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncMessageFilter);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_SYNC_MESSAGE_FILTER_H_