The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f38cfe3c3534c294e76977a13298b8491ba034a8

commit f38cfe3c3534c294e76977a13298b8491ba034a8
Author: Jennifer Apacible <apacible@chromium.org>
Date: Tue Jan 30 16:52:14 2018

[Media] Clean up interstitial CSS.

Only one interstitial (of media remoting and picture in picture) will
be shown at a time. This change renames IDs for elements in the
interstitial element with the same styling.

This change also pulls out the CSS into a separate file, per TODO.

Expected further work here includes some more styling updates with
an interstitial icon for picture in picture.

BUG:  805516 
Change-Id: I6c2151f2166b4dbbf2aaa0be83f8492369008a11
Reviewed-on: https://chromium-review.googlesource.com/890025
Reviewed-by: Mounir Lamouri (slow) <mlamouri@chromium.org>
Reviewed-by: Xiangjun Zhang <xjz@chromium.org>
Commit-Queue: apacible <apacible@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532917}
[modify] https://crrev.com/f38cfe3c3534c294e76977a13298b8491ba034a8/third_party/WebKit/LayoutTests/media/media-controls.js
[modify] https://crrev.com/f38cfe3c3534c294e76977a13298b8491ba034a8/third_party/WebKit/Source/core/html/media/MediaRemotingInterstitial.cpp
[modify] https://crrev.com/f38cfe3c3534c294e76977a13298b8491ba034a8/third_party/WebKit/Source/core/html/media/PictureInPictureInterstitial.cpp
[modify] https://crrev.com/f38cfe3c3534c294e76977a13298b8491ba034a8/third_party/WebKit/Source/modules/media_controls/MediaControlsResourceLoader.cpp
[modify] https://crrev.com/f38cfe3c3534c294e76977a13298b8491ba034a8/third_party/WebKit/Source/modules/media_controls/MediaControlsResourceLoader.h
[modify] https://crrev.com/f38cfe3c3534c294e76977a13298b8491ba034a8/third_party/WebKit/Source/modules/media_controls/resources/legacyMediaControls.css
[add] https://crrev.com/f38cfe3c3534c294e76977a13298b8491ba034a8/third_party/WebKit/Source/modules/media_controls/resources/mediaInterstitials.css
[modify] https://crrev.com/f38cfe3c3534c294e76977a13298b8491ba034a8/third_party/WebKit/Source/modules/media_controls/resources/media_controls_resources.grd

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0d8bdd5a4f7c3d09f99d78918f22d61022c5e002

commit 0d8bdd5a4f7c3d09f99d78918f22d61022c5e002
Author: Jennifer Apacible <apacible@chromium.org>
Date: Fri Feb 09 04:07:11 2018

[Media] Add PiP icon to interstitial.

Includes some relevant clean up for picture in picture and media remoting
interstitials.

BUG:  805516 
Change-Id: Idc8eb5553120228ac8c9b36c029963ef01cf4628
Reviewed-on: https://chromium-review.googlesource.com/906835
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Xiangjun Zhang <xjz@chromium.org>
Commit-Queue: apacible <apacible@chromium.org>
Cr-Commit-Position: refs/heads/master@{#535622}
[modify] https://crrev.com/0d8bdd5a4f7c3d09f99d78918f22d61022c5e002/third_party/WebKit/LayoutTests/media/media-controls.js
[modify] https://crrev.com/0d8bdd5a4f7c3d09f99d78918f22d61022c5e002/third_party/WebKit/Source/core/html/media/MediaRemotingInterstitial.cpp
[modify] https://crrev.com/0d8bdd5a4f7c3d09f99d78918f22d61022c5e002/third_party/WebKit/Source/core/html/media/MediaRemotingInterstitial.h
[modify] https://crrev.com/0d8bdd5a4f7c3d09f99d78918f22d61022c5e002/third_party/WebKit/Source/core/html/media/PictureInPictureInterstitial.cpp
[modify] https://crrev.com/0d8bdd5a4f7c3d09f99d78918f22d61022c5e002/third_party/WebKit/Source/core/html/media/PictureInPictureInterstitial.h
[modify] https://crrev.com/0d8bdd5a4f7c3d09f99d78918f22d61022c5e002/third_party/WebKit/Source/modules/media_controls/resources/mediaInterstitials.css
[modify] https://crrev.com/0d8bdd5a4f7c3d09f99d78918f22d61022c5e002/third_party/WebKit/Source/modules/media_controls/resources/modernMediaControls.css