Remove RefBase from the extractor API

- Add MetaDataBase base class that MetaData derives from, but which
  does not derive from RefBase.
- MediaBuffer::meta_data() now returns a MetaDataBase& rather than an
  sp<MetaData>
- Rename MediaSourceBase to MediaTrack.
- MediaSource no longer derives from MediaSourceBase (or MediaTrack)
- MediaTrack::getFormat(), MediaExtractor::getTrackMetaData() and
  MediaExtractor::getMetaData() all take a MetaDataBase& parameter that
  they fill out, rather than returning a MetaData directly (the
  corresponding methods on MediaSource and RemoteMediaExtractor continue
  to return MetaData)

Bug: 67908544
Test: CTS MediaPlayerTest, DecoderTest, EncodeDecodeTest, manually record video

Change-Id: Ib531ab309061290be33d40d6100c9a8127e22083
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerDecoder.cpp b/media/libmediaplayerservice/nuplayer/NuPlayerDecoder.cpp
index 88594d2..2a08f62 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerDecoder.cpp
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerDecoder.cpp
@@ -1071,7 +1071,7 @@
                     codecBuffer->setRange(0, mediaBuf->size());
                     memcpy(codecBuffer->data(), mediaBuf->data(), mediaBuf->size());
 
-                    sp<MetaData> meta_data = mediaBuf->meta_data();
+                    MetaDataBase &meta_data = mediaBuf->meta_data();
                     cryptInfo = NuPlayerDrm::getSampleCryptoInfo(meta_data);
                 } else { // No mediaBuf
                     ALOGE("onInputBufferFetched: buffer->data()/mediaBuf are NULL for %p",