Define/update structure and gamepad messages between renderer and browser.

content/common/gamepad_messages.h

 // Copyright (c) 2011 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.
 
 // Multiply-included message file, no include guard.
 
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_param_traits.h"
 #include "ipc/ipc_platform_file.h"
 #include "base/shared_memory.h"
 
 #define IPC_MESSAGE_START GamepadMsgStart
 
 // Messages sent from the renderer to the browser.
 
 // Asks the browser process to start polling, and return a shared memory
-// handles that will hold the (triple-buffered) data from the hardware.
-// The number of Starts should match the number of Stops (below).
+// handles that will hold the data from the hardware. See
+// gamepad_hardware_buffer.h for a description of how synchronization is
+// handled. The number of Starts should match the number of Stops.
 IPC_SYNC_MESSAGE_CONTROL0_1(GamepadHostMsg_StartPolling,
                             base::SharedMemoryHandle /* handle */)
 
 IPC_SYNC_MESSAGE_CONTROL0_0(GamepadHostMsg_StopPolling)
-
-
-// Messages sent from browser to renderer.
-
-IPC_MESSAGE_CONTROL1(GamepadMsg_Updated,
-                     int /* read_buffer_index */)