Unhide the android.media.[Media]DataSource interface.

This allows apps to implement MediaDataSource, which is modeled on
stagefright's DataSource, to supply media data to the framework. This
was already implemented for MediaExtractor, but it was renamed from
DataSource.

MediaExtractor, MediaPlayer and MediaMetadataRetriever each have a new
overload: #setDataSource(android.media.MediaDataSource)

Only NuPlayer supports this new data source.

The change introduces:
 * IDataSource:        The binder interface for DataSource.
 * JMediaDataSource:   The native counterpart to the java interface. It
                       implements IDataSource.
 * CallbackDataSource: A stagefright DataSource that wraps an
                       IDataSource.

Change-Id: Ib3c944b49cc8a792c8eb9c85e5015c07f298ebc1
diff --git a/include/media/MediaMetadataRetrieverInterface.h b/include/media/MediaMetadataRetrieverInterface.h
index 38dbb20..df6c7d6 100644
--- a/include/media/MediaMetadataRetrieverInterface.h
+++ b/include/media/MediaMetadataRetrieverInterface.h
@@ -25,7 +25,8 @@
 
 namespace android {
 
-struct IMediaHTTPService;
+class DataSource;
+class IMediaHTTPService;
 
 // Abstract base class
 class MediaMetadataRetrieverBase : public RefBase
@@ -40,6 +41,7 @@
             const KeyedVector<String8, String8> *headers = NULL) = 0;
 
     virtual status_t    setDataSource(int fd, int64_t offset, int64_t length) = 0;
+    virtual status_t setDataSource(const sp<DataSource>& source) = 0;
     virtual VideoFrame* getFrameAtTime(int64_t timeUs, int option) = 0;
     virtual MediaAlbumArt* extractAlbumArt() = 0;
     virtual const char* extractMetadata(int keyCode) = 0;