The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c54ab7cbb7e628b3c48452b6c4c8c931f7d02871

commit c54ab7cbb7e628b3c48452b6c4c8c931f7d02871
Author: Tommy Steimel <steimel@chromium.org>
Date: Fri Feb 16 04:24:24 2018

Show audio controls when video tag has only audio track

This CL makes CSS and structural changes to audio-track-only videos to
make the controls look like audio controls. This solves an issue where
the controls are not visible/usable on MediaDocument for audio files,
since MediaDocument uses a video tag with an audio source.

This change only applies for modern media controls.

Bug:  811377 
Change-Id: Ic73f65585c19047dec1d5904b50c7c4be496c5f5
Reviewed-on: https://chromium-review.googlesource.com/917610
Commit-Queue: Tommy Steimel <steimel@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537195}
[add] https://crrev.com/c54ab7cbb7e628b3c48452b6c4c8c931f7d02871/third_party/WebKit/LayoutTests/media/controls/modern/video-tag-with-only-audio-looks-like-audio-tag.html
[modify] https://crrev.com/c54ab7cbb7e628b3c48452b6c4c8c931f7d02871/third_party/WebKit/LayoutTests/media/media-controls.js
[modify] https://crrev.com/c54ab7cbb7e628b3c48452b6c4c8c931f7d02871/third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.cpp
[modify] https://crrev.com/c54ab7cbb7e628b3c48452b6c4c8c931f7d02871/third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.h
[modify] https://crrev.com/c54ab7cbb7e628b3c48452b6c4c8c931f7d02871/third_party/WebKit/Source/modules/media_controls/elements/MediaControlTimelineElement.cpp
[modify] https://crrev.com/c54ab7cbb7e628b3c48452b6c4c8c931f7d02871/third_party/WebKit/Source/modules/media_controls/resources/modernMediaControls.css
[modify] https://crrev.com/c54ab7cbb7e628b3c48452b6c4c8c931f7d02871/third_party/WebKit/Source/modules/media_controls/resources/modernMediaControls_timeline.css