Do we have stats on how many users have used the flag to force the old behavior?  I'm assuming it's a very small number, but perhaps worth checking.

Mark and I checked Analytics, and there are a very small number of users on
52 & 53 who are using the old extension, so I'm not too worried there.  And
according to "life of a Chrome feature," once our thing is baked we're
supposed to remove the flag.

If you remove the flag, how would it be possible to remove the "Cast..." item from page context menu? This functionality isn't used by the majority of users so it shouldn't clutter the menu in order not to undermine simplicity of Chrome/Chromium.

I fully agree it's the right thing to do per normal Chrome process, and was only looking to understand the worst-case possible impact for users who had a specific need for something in the old extension.  #2 data suggests no concern here.

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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