Nice to have

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/aed2fbc98cd244a46543a52e214cf7741351b07e

commit aed2fbc98cd244a46543a52e214cf7741351b07e
Author: Takumi Fujimoto <takumif@chromium.org>
Date: Thu Sep 13 23:10:45 2018

Depress the Cast toolbar icon when showing Media Remoting dialog

Put the Cast toolbar icon in pressed state while showing the Media
Remoting dialog.

Bug: 854374
Change-Id: Ie75f7905e7c796375ec85075a56bbdf15c73d36c
Reviewed-on: https://chromium-review.googlesource.com/1191063
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Commit-Queue: mark a. foltz <mfoltz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591197}
[modify] https://crrev.com/aed2fbc98cd244a46543a52e214cf7741351b07e/chrome/browser/ui/views/media_router/media_remoting_dialog_view.cc
[modify] https://crrev.com/aed2fbc98cd244a46543a52e214cf7741351b07e/chrome/browser/ui/views/media_router/media_remoting_dialog_view.h

We still have to depress the icon when the cloud services dialog is shown. It's a bit complicated because that dialog is shown via the context menu, and when the context menu gets hidden it resets the icon state. 

Moving to M-72 as this is not in anyone's queue at the moment.