drm: use DrmSessionManager for session resource managing.

Bug: 19265536
Change-Id: Ie35184f99c51e7bd94d7c826ffb8e89040a81905
diff --git a/media/libmediaplayerservice/Drm.h b/media/libmediaplayerservice/Drm.h
index 0e1eb2c..0cea639 100644
--- a/media/libmediaplayerservice/Drm.h
+++ b/media/libmediaplayerservice/Drm.h
@@ -28,6 +28,7 @@
 
 struct DrmFactory;
 struct DrmPlugin;
+struct DrmSessionClientInterface;
 
 struct Drm : public BnDrm,
              public IBinder::DeathRecipient,
@@ -138,6 +139,8 @@
 
     status_t mInitCheck;
 
+    sp<DrmSessionClientInterface> mDrmSessionClient;
+
     sp<IDrmClient> mListener;
     mutable Mutex mEventLock;
     mutable Mutex mNotifyLock;