Poll for Display rotation on Android 4.0 and 4.1 when needed.

content/common/screen_orientation_messages.h

 // Copyright 2014 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 screen orientation.
 // Multiply-included message file, hence no include guard.
 
 #include "content/common/content_export.h"
 #include "ipc/ipc_message_macros.h"
 #include "third_party/WebKit/public/platform/WebLockOrientationError.h"
@@ skipping 44 matching lines @@
 // |request_id| that will have to be passed back to the renderer process when
 // notifying about a success or error (see ScreenOrientationMsg_LockError and
 // ScreenOrientationMsg_LockSuccess).
 IPC_MESSAGE_ROUTED2(ScreenOrientationHostMsg_LockRequest,
                     blink::WebScreenOrientationLockType, /* orientation */
                     int /* request_id */)
 
 // The renderer process requests the browser process to unlock the screen
 // orientation.
 IPC_MESSAGE_ROUTED0(ScreenOrientationHostMsg_Unlock)
+
+// The renderer process is now using the Screen Orientation API and informs the
+// browser process that it should start accurately listening to the screen
+// orientation if it wasn't already.
+// This is only expected to be acted upon when the underlying platform requires
+// heavy work in order to accurately know the screen orientation.
+IPC_MESSAGE_CONTROL0(ScreenOrientationHostMsg_StartListening)
+
+// The renderer process is no longer using the Screen Orientation API and
+// informs the browser process that it can stop accurately listening to the
+// screen orientation if no other process cares about it.
+// This is only expected to be acted upon when the underlying platform requires
+// heavy work in order to accurately know the screen orientation.
+IPC_MESSAGE_CONTROL0(ScreenOrientationHostMsg_StopListening)