Improve NDK to framework DataSource adaptor

+ propagate DataSource::flags values
+ keep reference to internal DataSource to avoid use-after-free

Bug: 109928575
Test: android.media.cts.NativeDecoderTest#testExtractor
Change-Id: I8c696fa510195ed616b117135aea3911c88e44bd
diff --git a/media/ndk/NdkMediaDataSourcePriv.h b/media/ndk/NdkMediaDataSourcePriv.h
index 3b0aa59..8a5423c 100644
--- a/media/ndk/NdkMediaDataSourcePriv.h
+++ b/media/ndk/NdkMediaDataSourcePriv.h
@@ -44,6 +44,7 @@
     NdkDataSource(AMediaDataSource *);
 
     virtual status_t initCheck() const;
+    virtual uint32_t flags();
     virtual ssize_t readAt(off64_t offset, void *data, size_t size);
     virtual status_t getSize(off64_t *);
     virtual String8 toString();