VTVDA and DXVA now both output frames that outlive themselves. The only remaining VDA I'm not sure about is the ChromeOS one and I can't easily test it.  dalecurtis@, posciak@ do you know?

Since we've enabled suspend on all platforms I think we can remove this now.

(along with DECODER_OWNS_FRAME metadata)

Perfect, will remove!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d16bb3ef495de7c6bdeb57d44c5353273becdcda

commit d16bb3ef495de7c6bdeb57d44c5353273becdcda
Author: watk <watk@chromium.org>
Date: Tue Apr 25 01:18:31 2017

media: Discard the previous decoder immediately on fallback

Previously, after falling back to another decoder, we had to keep the
old one alive in case it owned frames that were currently being
displayed.

Now all decoders produce frames that outlive themselves, so we can
safely delete the decoder as soon as we no longer need it.

This change also includes deletion of a related, but now unused,
VideoFrame metadata value called DECODER_OWNS_FRAME.

BUG= 663988 

Review-Url: https://codereview.chromium.org/2841553003
Cr-Commit-Position: refs/heads/master@{#466854}

[modify] https://crrev.com/d16bb3ef495de7c6bdeb57d44c5353273becdcda/media/base/video_frame_metadata.h
[modify] https://crrev.com/d16bb3ef495de7c6bdeb57d44c5353273becdcda/media/blink/webmediaplayer_impl.cc
[modify] https://crrev.com/d16bb3ef495de7c6bdeb57d44c5353273becdcda/media/filters/decoder_stream.cc
[modify] https://crrev.com/d16bb3ef495de7c6bdeb57d44c5353273becdcda/media/filters/decoder_stream.h
[modify] https://crrev.com/d16bb3ef495de7c6bdeb57d44c5353273becdcda/media/filters/gpu_video_decoder.cc
[modify] https://crrev.com/d16bb3ef495de7c6bdeb57d44c5353273becdcda/media/filters/video_frame_stream_unittest.cc
[modify] https://crrev.com/d16bb3ef495de7c6bdeb57d44c5353273becdcda/media/renderers/video_overlay_factory.cc