[DeviceService] Mojofy left screen orientation IPC messages.

device/screen_orientation/public/interfaces/screen_orientation.mojom

Index: device/screen_orientation/public/interfaces/screen_orientation.mojom
diff --git a/device/screen_orientation/public/interfaces/screen_orientation.mojom b/device/screen_orientation/public/interfaces/screen_orientation.mojom
index 0cc849e642426c39224521d45b6d033f7077d7a2..f625d2e7806bc80a0358003ad94e992a5ee54d74 100644
--- a/device/screen_orientation/public/interfaces/screen_orientation.mojom
+++ b/device/screen_orientation/public/interfaces/screen_orientation.mojom
@@ -11,3 +11,19 @@ interface ScreenOrientation {
     (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();
+};