MediaBuffer: ABuffer will release MediaBuffer when it's destructed.

Bug: 17454455
Change-Id: Ia423bcc2e1fa39137f114eac44912ed15357bb99
diff --git a/media/libmediaplayerservice/nuplayer/GenericSource.cpp b/media/libmediaplayerservice/nuplayer/GenericSource.cpp
index 511871d..a0870fd 100644
--- a/media/libmediaplayerservice/nuplayer/GenericSource.cpp
+++ b/media/libmediaplayerservice/nuplayer/GenericSource.cpp
@@ -1097,8 +1097,8 @@
     if (mIsWidevine && !audio) {
         // data is already provided in the buffer
         ab = new ABuffer(NULL, mb->range_length());
-        ab->meta()->setPointer("mediaBuffer", mb);
         mb->add_ref();
+        ab->setMediaBufferBase(mb);
     } else {
         ab = new ABuffer(outLength);
         memcpy(ab->data(),