[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..c54218843371fb8fb00356a0c42b2c0ab87a4897 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();
 };
+
+// ScreenOrientationListener 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 ScreenOrientationListener {
+  // 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.
+  Start();
+  
+  // 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.
+  Stop();
+};