Not a priority for now; we can revisit once we've done more MRP open-sourcing.

We'll never revisit if it's marked WontFix.  Marking P3.

apacible@ pointed out in code review:

"wrt ungating cloud services - should we check if kLoadMediaRouterComponentExtension is true if it's a chromium build? Otherwise, if the user is signed in and opens the dialog (with no devices) but is expecting cloud sinks, they may be confused.

I don't know actual numbers of chromium usage, but I remember in uni we had chromium preinstalled on our linux desktops and needed special admin permissions to install other software (i.e. Chrome). I would probably have run into the aforementioned case if I didn't know about the kLoadMediaRouterComponentExtension flag. :)"

The issue I see with checking the flag is that the flag could be disabled and the developer or user could have loaded an alternate extension.  However, they would never be able to use cloud screens provided by that extension.

If there's no component at all (i.e. nothing implementing MRPM) maybe we could message the user?

Could we surface an 'issue' if there's no component at all?

Yup.  We do this already in media_router_ui.cc for e.g. timeouts.

https://cs.chromium.org/chromium/src/chrome/browser/ui/webui/media_router/media_router_ui.cc?rcl=0&l=634

Cool, SGTM.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ac0030f5d07e66752b93695bc373bcb55ab26602

commit ac0030f5d07e66752b93695bc373bcb55ab26602
Author: mfoltz <mfoltz@chromium.org>
Date: Fri Oct 28 21:16:52 2016

[Media Router] Update Media Router flags post-launch.

- Remove --media-router flag as this functionality has shipped
  ( crbug.com/651255 )

- Remove lots of GOOGLE_CHROME_BUILD #ifdefs around cloud services
  ( crbug.com/646171 )

- Adds a --load-media-router-component-extension flag to control loading of the
  Media Router component.  This is default on in Chrome and default off in
  Chromium.  ( crbug.com/646170 )

BUG= 646170 , 646171 , 651255 

Review-Url: https://codereview.chromium.org/2451573003
Cr-Commit-Position: refs/heads/master@{#428493}

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