Add FramesSentAsOverlay UMA metric to AVDA.

media/gpu/android_video_decode_accelerator.cc

Index: media/gpu/android_video_decode_accelerator.cc
diff --git a/media/gpu/android_video_decode_accelerator.cc b/media/gpu/android_video_decode_accelerator.cc
index 9ce73d4c50030376573662614508f3492e9ae99e..7a0326297acc1250d255ad875f684b18bd39ed55 100644
--- a/media/gpu/android_video_decode_accelerator.cc
+++ b/media/gpu/android_video_decode_accelerator.cc
@@ -939,6 +939,7 @@ void AndroidVideoDecodeAccelerator::SendDecodedFrameToClient(
   }
 
   const bool allow_overlay = strategy_->ArePicturesOverlayable();
+  UMA_HISTOGRAM_BOOLEAN("Media.AVDA.FrameSentAsOverlay", allow_overlay);
   Picture picture(picture_buffer_id, bitstream_id, gfx::Rect(size_),
                   allow_overlay);
   picture.set_size_changed(size_changed);