refactor getTrackInfo()

(this is in preparation for supporting other cc source)

- split into two methods: getTrackCount() and getTrackInfo()

- move track info parcelling to NuPlayer

- parcel in the mime type of the subtitle format

Bug: 15470448
Change-Id: If00724d8c3a2b2319cb9c5f29d3fe76347bfe947
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerSource.h b/media/libmediaplayerservice/nuplayer/NuPlayerSource.h
index 11279fc..f5a1d6d 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerSource.h
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerSource.h
@@ -72,8 +72,12 @@
         return INVALID_OPERATION;
     }
 
-    virtual status_t getTrackInfo(Parcel* /* reply */) const {
-        return INVALID_OPERATION;
+    virtual size_t getTrackCount() const {
+        return 0;
+    }
+
+    virtual sp<AMessage> getTrackInfo(size_t /* trackIndex */) const {
+        return NULL;
     }
 
     virtual status_t selectTrack(size_t /* trackIndex */, bool /* select */) {