Send input event IPCs directly from the UI thread

ipc/ipc_sync_message_filter.cc

 // 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.
 
 #include "ipc/ipc_sync_message_filter.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "ipc/ipc_channel.h"
 #include "ipc/ipc_sync_message.h"
 
 namespace IPC {
 
 bool SyncMessageFilter::Send(Message* message) {
   if (!message->is_sync()) {
     {
       base::AutoLock auto_lock(lock_);
-      if (sender_ && is_channel_send_thread_safe_) {
-        sender_->Send(message);
-        return true;
-      } else if (!io_task_runner_.get()) {
+      if (!io_task_runner_.get()) {
         pending_messages_.push_back(message);
         return true;
       }
     }
     io_task_runner_->PostTask(
         FROM_HERE,
         base::Bind(&SyncMessageFilter::SendOnIOThread, this, message));
     return true;
   }
 
@@ skipping 74 matching lines @@
                               "SyncMessageFilter::OnMessageReceived",
                               (*iter)->done_event);
       (*iter)->done_event->Signal();
       return true;
     }
   }
 
   return false;
 }
 
+bool SyncMessageFilter::SendNow(std::unique_ptr<Message> message) {
+  if (!message->is_sync()) {
+    base::AutoLock auto_lock(lock_);
+    if (sender_ && is_channel_send_thread_safe_) {
+      sender_->Send(message.release());
+      return true;
+    }
+  }
+
+  // Fall back on default Send behavior.
+  return Send(message.release());
+}
+
 SyncMessageFilter::SyncMessageFilter(base::WaitableEvent* shutdown_event,
                                      bool is_channel_send_thread_safe)
     : sender_(NULL),
       is_channel_send_thread_safe_(is_channel_send_thread_safe),
       listener_task_runner_(base::ThreadTaskRunnerHandle::Get()),
       shutdown_event_(shutdown_event) {
 }
 
 SyncMessageFilter::~SyncMessageFilter() {
 }
@@ skipping 19 matching lines @@
   for (PendingSyncMessages::iterator iter = pending_sync_messages_.begin();
        iter != pending_sync_messages_.end(); ++iter) {
     TRACE_EVENT_FLOW_BEGIN0(TRACE_DISABLED_BY_DEFAULT("ipc.flow"),
                             "SyncMessageFilter::SignalAllEvents",
                             (*iter)->done_event);
     (*iter)->done_event->Signal();
   }
 }
 
 }  // namespace IPC