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

content/common/gamepad_messages.h

Index: content/common/gamepad_messages.h
diff --git a/content/common/gamepad_messages.h b/content/common/gamepad_messages.h
index a93a140f8a6e35a530feda4927e33407b7294bd8..65478b0db9097024092ff32939411bcf7ca47378 100644
--- a/content/common/gamepad_messages.h
+++ b/content/common/gamepad_messages.h
@@ -14,15 +14,10 @@
 // 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 */)