MediaPlayer2: use DataSource to replace IDataSource.

Also fix deadlock by always posting notification to NuPlayer2Driver's
looper.
Test: MediaPlayer2 can play callback source.
Bug: 63934228

Change-Id: Ie27bc0038bcc07ffef5c610662db3fcb5df7aec4
diff --git a/media/libmedia/nuplayer2/GenericSource.cpp b/media/libmedia/nuplayer2/GenericSource.cpp
index f8bc4f1..acd54a1 100644
--- a/media/libmedia/nuplayer2/GenericSource.cpp
+++ b/media/libmedia/nuplayer2/GenericSource.cpp
@@ -364,7 +364,9 @@
     if (mLooper == NULL) {
         mLooper = new ALooper;
         mLooper->setName("generic");
-        mLooper->start();
+        mLooper->start(false, /* runOnCallingThread */
+                       true,  /* canCallJava */
+                       PRIORITY_DEFAULT);
 
         mLooper->registerHandler(this);
     }