The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5e20cba450560f9baa12744ac3daaab7b6c045b2

commit 5e20cba450560f9baa12744ac3daaab7b6c045b2
Author: Xiangjun Zhang <xjz@chromium.org>
Date: Wed Jan 10 19:54:56 2018

Add toast for Media Remoting.

This CL added a toast on media remoting UI. When switching a media
remoting session to mirroring, a message will be shown on the video for
5 seconds to inform the user.

Bug:  797327 
Change-Id: Ib61e3d910bd77a6bf2e3b8942ce740e741816c8f
Reviewed-on: https://chromium-review.googlesource.com/843453
Commit-Queue: Xiangjun Zhang <xjz@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Xiaohan Wang <xhwang@chromium.org>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#528395}
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/content/app/strings/content_strings.grd
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/content/child/blink_platform_impl.cc
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/content/renderer/media/webmediaplayer_ms_unittest.cc
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/media/base/media_observer.h
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/media/blink/webmediaplayer_impl.cc
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/media/blink/webmediaplayer_impl.h
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/media/blink/webmediaplayer_impl_unittest.cc
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/media/remoting/renderer_controller.cc
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/media/remoting/renderer_controller_unittest.cc
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/third_party/WebKit/Source/core/html/media/HTMLAudioElement.h
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/third_party/WebKit/Source/core/html/media/HTMLVideoElement.cpp
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/third_party/WebKit/Source/core/html/media/HTMLVideoElement.h
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/third_party/WebKit/Source/core/html/media/MediaRemotingInterstitial.cpp
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/third_party/WebKit/Source/core/html/media/MediaRemotingInterstitial.h
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/third_party/WebKit/Source/modules/media_controls/resources/legacyMediaControls.css
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/third_party/WebKit/Source/modules/remoteplayback/RemotePlayback.cpp
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/third_party/WebKit/public/platform/WebLocalizedString.h
[modify] https://crrev.com/5e20cba450560f9baa12744ac3daaab7b6c045b2/third_party/WebKit/public/platform/WebMediaPlayerClient.h