It seems to me one of the benefits of casting vs. local playback is to retain control of your local browser window and multitask while the media plays elsewhere.  Playing the media fullscreen doesn't really allow that (or requires an extra step to get back to the browser window).  Does this proposal align with the feature PRD?

I created this specifically for https://chromium-review.googlesource.com/c/chromium/src/+/731669 instead of tagging it to the launch bug as Anna's original change had it.

And to be clear this is fullscreen after the capture is started, so it's fullscreen-in-tab, not actual fullscreen.

My description may be off from the PRD says, but I believe this was all planned work and in fact the only thing left blocking the launch.

Okay, fullscreen-in-tab makes much more sense.  Maybe edit the original description to clarify.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06

commit 6a19ba34ce27c038df1abb91cf72c9b01ae8fc06
Author: Adam Parker <amp@chromium.org>
Date: Tue Jan 09 00:47:28 2018

[Local Media Casting] Automatically fullscreen local media casting video files.

This change adds back a previously removed blink API on WebElement to
fullscreen an element.

This API is then wired up to media router UI and the local media casting flow to
fullscreen the first video element as soon as it is loaded.

Bug:  777005 
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_site_isolation
Change-Id: I3d4e24c2a8d45edbfa612312a21053086750df11
Reviewed-on: https://chromium-review.googlesource.com/731669
Commit-Queue: Adam Parker <amp@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#527835}
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/chrome/browser/ui/webui/media_router/media_router_ui.cc
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/chrome/browser/ui/webui/media_router/media_router_ui.h
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/chrome/test/media_router/BUILD.gn
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/chrome/test/media_router/media_router_e2e_browsertest.cc
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/chrome/test/media_router/media_router_e2e_ui_browsertest.cc
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/chrome/test/media_router/media_router_integration_browsertest.cc
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/chrome/test/media_router/media_router_integration_browsertest.h
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/chrome/test/media_router/resources/local_media_sink.json
[add] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/chrome/test/media_router/resources/local_media_sink_route_fail.json
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/content/public/app/mojo/content_renderer_manifest.json
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/content/public/common/BUILD.gn
[add] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/content/public/common/fullscreen_video_element.mojom
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/content/renderer/render_frame_impl.cc
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/content/renderer/render_frame_impl.h
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/third_party/WebKit/Source/core/exported/WebElement.cpp
[modify] https://crrev.com/6a19ba34ce27c038df1abb91cf72c9b01ae8fc06/third_party/WebKit/public/web/WebElement.h