b/15757378 Expose APIs for listening to active sessions

This allows apps that are registered notification listeners to
listen to the set of active sessions.

Change-Id: I1e108951a5049d138208e88b155c0ec9b95fbdb0
diff --git a/services/core/java/com/android/server/media/MediaSessionService.java b/services/core/java/com/android/server/media/MediaSessionService.java
index 685717f..c0b7d68 100644
--- a/services/core/java/com/android/server/media/MediaSessionService.java
+++ b/services/core/java/com/android/server/media/MediaSessionService.java
@@ -383,6 +383,9 @@
             // You may not access another user's content as an enabled listener.
             return false;
         }
+        if (DEBUG) {
+            Log.d(TAG, "Checking if enabled notification listener " + compName);
+        }
         if (compName != null) {
             final String enabledNotifListeners = Settings.Secure.getStringForUser(mContentResolver,
                     Settings.Secure.ENABLED_NOTIFICATION_LISTENERS,