Add a small hook to support gapless in AAH.

Change-Id: Ie07eca6b45142bdd83412ee0e38d732a4c355630
diff --git a/include/media/MediaPlayerInterface.h b/include/media/MediaPlayerInterface.h
index 518948c..b7bee3f 100644
--- a/include/media/MediaPlayerInterface.h
+++ b/include/media/MediaPlayerInterface.h
@@ -150,16 +150,16 @@
     virtual status_t    setParameter(int key, const Parcel &request) = 0;
     virtual status_t    getParameter(int key, Parcel *reply) = 0;
 
-    // Right now, only the AAX TX player supports this functionality.  For now,
-    // provide default implementations which indicate a lack of support for this
-    // functionality to make life easier for all of the other media player
-    // maintainers out there.
+    // default no-op implementation of optional extensions
     virtual status_t setRetransmitEndpoint(const struct sockaddr_in* endpoint) {
         return INVALID_OPERATION;
     }
     virtual status_t getRetransmitEndpoint(struct sockaddr_in* endpoint) {
         return INVALID_OPERATION;
     }
+    virtual status_t setNextPlayer(const sp<MediaPlayerBase>& next) {
+        return OK;
+    }
 
     // Invoke a generic method on the player by using opaque parcels
     // for the request and reply.