[DeviceService] Mojofy left screen orientation IPC messages.

device/screen_orientation/public/interfaces/screen_orientation.mojom

 // Copyright 2016 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.
 
 module device.mojom;
 
 import "device/screen_orientation/public/interfaces/screen_orientation_lock_types.mojom";
 
 interface ScreenOrientation {
   LockOrientation(ScreenOrientationLockType orientation) =>
     (ScreenOrientationLockResult result);
   UnlockOrientation();
 };
+
+// ScreenOrientationAccurate is expected to be used when the platform requires
+// heavy work in order to accurately know the screen orientation.
+// For example, on Android, this is required for Jelly Bean, where there is no
+// API to be notified of a screen orientation change of 180 degrees.
+interface ScreenOrientationAccurate {

[blundell, 2016/12/20 13:39:18]

I suggest we rename this ScreenOrientationListener.

[leonhsl(Using Gerrit), 2016/12/21 02:48:36]

Done.

+  // 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.
+  StartListening();

[blundell, 2016/12/20 13:39:18]

We can rename these to Start and Stop. So we'll have calls like e.g.

listener_->Start()

[leonhsl(Using Gerrit), 2016/12/21 02:48:36]

Done.

+  
+  // 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.
+  StopListening();
+};