Add hints for potential overlay promotion on android.

media/base/video_frame_metadata.h

Index: media/base/video_frame_metadata.h
diff --git a/media/base/video_frame_metadata.h b/media/base/video_frame_metadata.h
index 23b40ac3dfd712bd3636f709c0955911f72d86fd..40d9d1aad3a14a207e018f0944596ed56e94edf5 100644
--- a/media/base/video_frame_metadata.h
+++ b/media/base/video_frame_metadata.h
@@ -110,6 +110,12 @@ class MEDIA_EXPORT VideoFrameMetadata {
     // Indicates that the frame is rotated.
     ROTATION,
 
+    // Android only: if set, then this frame is not suitable for overlay, even
+    // if ALLOW_OVERLAY is set.  However, it allows us to process the overlay
+    // to see if it would have been promoted, if it were backed by a SurfaceView
+    // instead.  This lets us figure out when SurfaceViews are appropriate.
+    SURFACE_TEXTURE,
+
     NUM_KEYS
   };