Enable adaptive playback for spitzer, use conservative size.

media/video/video_decode_accelerator.h

Index: media/video/video_decode_accelerator.h
diff --git a/media/video/video_decode_accelerator.h b/media/video/video_decode_accelerator.h
index cc01eaf20fed957dda230671c719acf341fc299d..6722e2b97193157308fc43e68da692a01cc293bf 100644
--- a/media/video/video_decode_accelerator.h
+++ b/media/video/video_decode_accelerator.h
@@ -122,6 +122,9 @@ class MEDIA_EXPORT VideoDecodeAccelerator {
     // an output SurfaceView on Android. It's only valid when not equal to
     // |kNoSurfaceID|.
     int surface_id = kNoSurfaceID;
+
+    // Coded size of the video frame hint, subject to change.
+    gfx::Size initial_expected_coded_size;
   };
 
   // Interface for collaborating with picture interface to provide memory for