upstream commit:

commit 62f07825ba11502b329716baddadea112c1837e5
Author: Michael Niedermayer <michael@niedermayer.cc>
Date:   Sat May 5 20:08:36 2018 +0200

bnreaks vp3 decoding for some our our layout test files (test_5.ogv):

webkit_layout_tests (with patch) Run on OS: 'Ubuntu-14.04'
Max shard duration: 0:12:26.267880 (shard #1)
Total tests: 79014
* Passed: 66455 (66404 expected, 51 unexpected)
* Skipped: 10140 (10140 expected, 0 unexpected)
* Failed: 2360 (2307 expected, >>>53 unexpected<<<)
* Flaky: 59 (58 expected, >>>1 unexpected<<<)
 
Unexpected Failures:
* external/wpt/html/semantics/embedded-content/media-elements/autoplay-with-broken-track.html
* external/wpt/html/semantics/embedded-content/media-elements/error-codes/error.html
* external/wpt/html/semantics/embedded-content/media-elements/event_canplay.html
* external/wpt/html/semantics/embedded-content/media-elements/event_canplay_noautoplay.html
* external/wpt/html/semantics/embedded-content/media-elements/event_canplaythrough.html
* external/wpt/html/semantics/embedded-content/media-elements/event_canplaythrough_noautoplay.html
* external/wpt/html/semantics/embedded-content/media-elements/event_loadeddata.html
* external/wpt/html/semantics/embedded-content/media-elements/event_loadeddata_noautoplay.html
* external/wpt/html/semantics/embedded-content/media-elements/event_order_canplay_canplaythrough.html
* external/wpt/html/semantics/embedded-content/media-elements/event_order_canplay_playing.html
* external/wpt/html/semantics/embedded-content/media-elements/event_order_loadedmetadata_loadeddata.html
* external/wpt/html/semantics/embedded-content/media-elements/event_pause.html
* external/wpt/html/semantics/embedded-content/media-elements/event_play.html
* external/wpt/html/semantics/embedded-content/media-elements/event_playing.html
* external/wpt/html/semantics/embedded-content/media-elements/event_playing_noautoplay.html
* external/wpt/html/semantics/embedded-content/media-elements/event_timeupdate.html
* external/wpt/html/semantics/embedded-content/media-elements/event_timeupdate_noautoplay.html
* external/wpt/html/semantics/embedded-content/media-elements/interfaces/TextTrack/activeCues.html
* external/wpt/html/semantics/embedded-content/media-elements/paused_false_during_play.html
* external/wpt/html/semantics/embedded-content/media-elements/ready-states/autoplay-with-slow-text-tracks.html
* external/wpt/html/semantics/embedded-content/media-elements/ready-states/autoplay.html
* external/wpt/html/semantics/embedded-content/media-elements/readyState_during_canplay.html
* external/wpt/html/semantics/embedded-content/media-elements/readyState_during_canplaythrough.html
* external/wpt/html/semantics/embedded-content/media-elements/readyState_during_loadeddata.html
* external/wpt/html/semantics/embedded-content/media-elements/readyState_during_playing.html
* external/wpt/html/semantics/embedded-content/media-elements/seeking/seek-to-currentTime.html
* external/wpt/html/semantics/embedded-content/media-elements/seeking/seek-to-max-value.htm
* external/wpt/html/semantics/embedded-content/media-elements/seeking/seek-to-negative-time.htm
* external/wpt/html/semantics/embedded-content/media-elements/track/track-element/track-active-cues.html
* external/wpt/html/semantics/embedded-content/media-elements/video_loop_base.html

Michael provided a patch, which will be cherry-picked into origin.  This bug tracks the upstream.