[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();
 };
+
+interface ScreenOrientationAccurate {

[mlamouri (slow - plz ping), 2016/12/15 10:30:56]

Can you add some documentation explaining why and when this is needed:
```
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.
```

Feel free to change :)

[leonhsl(Using Gerrit), 2016/12/16 03:12:00]

Acknowledged.

[leonhsl(Using Gerrit), 2016/12/19 09:41:22]

Done and Thanks!

+  // 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.

[mlamouri (slow - plz ping), 2016/12/15 10:30:57]

I think you can remove these last two lines (some for StopListening). The top
documentation should be enough.

[leonhsl(Using Gerrit), 2016/12/16 03:12:00]

Acknowledged.

[leonhsl(Using Gerrit), 2016/12/19 09:41:22]

Done.

+  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.
+  StopListening();
+};