Implement Device Orientation using shared memory in content/renderer.

content/common/device_orientation_messages.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.
 
 // IPC messages for device orientation.
 // Multiply-included message file, hence no include guard.
 
+#include "base/memory/shared_memory.h"
 #include "ipc/ipc_message_macros.h"
 
 #define IPC_MESSAGE_START DeviceOrientationMsgStart
 
+// 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 data from the hardware. See
+// device_motion_hardware_buffer.h for a description of how synchronization is
+// handled. The number of Starts should match the number of Stops.
+IPC_MESSAGE_CONTROL0(DeviceOrientationHostMsg_StartPolling)
+IPC_MESSAGE_CONTROL1(DeviceOrientationMsg_DidStartPolling,
+                     base::SharedMemoryHandle /* handle */)
+
+IPC_MESSAGE_CONTROL0(DeviceOrientationHostMsg_StopPolling)
+
+// TODO(timvolodine): remove the methods below once the Device Motion
+// is implemented.
+
 IPC_STRUCT_BEGIN(DeviceOrientationMsg_Updated_Params)
   // These fields have the same meaning as in content::Orientation.
   IPC_STRUCT_MEMBER(bool, can_provide_alpha)
   IPC_STRUCT_MEMBER(double, alpha)
   IPC_STRUCT_MEMBER(bool, can_provide_beta)
   IPC_STRUCT_MEMBER(double, beta)
   IPC_STRUCT_MEMBER(bool, can_provide_gamma)
   IPC_STRUCT_MEMBER(double, gamma)
   IPC_STRUCT_MEMBER(bool, can_provide_absolute)
   IPC_STRUCT_MEMBER(bool, absolute)
 IPC_STRUCT_END()
 
 // Messages sent from the browser to the renderer.
 
 // Notification that the device's orientation has changed.
 IPC_MESSAGE_ROUTED1(DeviceOrientationMsg_Updated,
                     DeviceOrientationMsg_Updated_Params)
 
 // Messages sent from the renderer to the browser.
 
 // A RenderView requests to start receiving device orientation updates.
 IPC_MESSAGE_CONTROL1(DeviceOrientationHostMsg_StartUpdating,
                      int /* render_view_id */)
 
 // A RenderView requests to stop receiving device orientation updates.
 IPC_MESSAGE_CONTROL1(DeviceOrientationHostMsg_StopUpdating,
                      int /* render_view_id */)