Going to assume that VP9 results changed slightly with this libvpx roll.  
 https://chromium.googlesource.com/chromium/src/+/2ca70a3e9835d0eafcdefb489a1bd6b6119bfee3.

Visual change is minor, so I will go ahead and update the reference image.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6d54e02b9d97dd583267a6591e63558a8e8be852

commit 6d54e02b9d97dd583267a6591e63558a8e8be852
Author: vmiura <vmiura@chromium.org>
Date: Tue May 09 22:23:28 2017

Bump revision number for _DirectComposition_Video_VP9 test.

The VP9 decoded image result slighly changed, which seems to be related
to a recent third_party/libvpx roll.

Bump the revision to regenerate the reference image.

TBR=kbr@chromium.org,jbauman@chromium.org
NOTRY=true
BUG= 720017 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2873733002
Cr-Commit-Position: refs/heads/master@{#470430}

[modify] https://crrev.com/6d54e02b9d97dd583267a6591e63558a8e8be852/content/test/gpu/gpu_tests/pixel_test_pages.py

 Issue 719970  has been merged into this issue.

This looks like it will roll green.