Adds listeners for changes to the list of active sessions

The listeners get notified when sessions are added, removed, or
reprioritized.

Change-Id: I7f3bfc84049719c3b9c19016c6bac92e1a5c3179
diff --git a/Android.mk b/Android.mk
index a1d91c3..8b0e556 100644
--- a/Android.mk
+++ b/Android.mk
@@ -306,14 +306,15 @@
 	media/java/android/media/IRemoteVolumeObserver.aidl \
 	media/java/android/media/IRingtonePlayer.aidl \
 	media/java/android/media/IVolumeController.aidl \
-        media/java/android/media/routeprovider/IRouteConnection.aidl \
-        media/java/android/media/routeprovider/IRouteProvider.aidl \
-        media/java/android/media/routeprovider/IRouteProviderCallback.aidl \
-        media/java/android/media/session/ISessionController.aidl \
-        media/java/android/media/session/ISessionControllerCallback.aidl \
-        media/java/android/media/session/ISession.aidl \
-        media/java/android/media/session/ISessionCallback.aidl \
-        media/java/android/media/session/ISessionManager.aidl \
+	media/java/android/media/routeprovider/IRouteConnection.aidl \
+	media/java/android/media/routeprovider/IRouteProvider.aidl \
+	media/java/android/media/routeprovider/IRouteProviderCallback.aidl \
+	media/java/android/media/session/IActiveSessionsListener.aidl \
+	media/java/android/media/session/ISessionController.aidl \
+	media/java/android/media/session/ISessionControllerCallback.aidl \
+	media/java/android/media/session/ISession.aidl \
+	media/java/android/media/session/ISessionCallback.aidl \
+	media/java/android/media/session/ISessionManager.aidl \
 	media/java/android/media/tv/ITvInputClient.aidl \
 	media/java/android/media/tv/ITvInputHardware.aidl \
 	media/java/android/media/tv/ITvInputHardwareCallback.aidl \