Remove MediaRouterAction

The new CastToolbarButton in the toolbar's trusted area is now enabled by
default, so this CL removes the old Media Router toolbar action that was
replaced by it.

MediaRouterActionController is still used by the new icon, and will be
renamed in a separate patch.

Bug: 919185
Change-Id: I95842e657379f823bd483d0a3da00015f76d8255
Reviewed-on: https://chromium-review.googlesource.com/c/1395419
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Takumi Fujimoto <takumif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634839}
24 files changed