[Media Router] Make MRUIService dispose its dependencies on MRMojoImpl in Shutdown()

[Media Router] Make MRUIService dispose its dependencies on MRMojoImpl in Shutdown()

Both MediaRouterUIService and MediaRouterMojoImpl are KeyedServices, and the
dependency from the former to the latter should be disposed in its Shutdown()
method. |action_controller_| is an observer to MediaRouterMojoImpl, so it needs
to be reset in Shutdown().

BUG=705216
Review-Url: https://codereview.chromium.org/2774383003
Cr-Commit-Position: refs/heads/master@{#459900}
(cherry picked from commit 6812c7313dd67fcfad6f95d4b5a91cf7dcfda06a)

Review-Url: https://codereview.chromium.org/2772343004 .
Cr-Commit-Position: refs/branch-heads/3053@{#3}
Cr-Branched-From: bba05f44fe583ffa69c22d36f91aaebe0ceea282-refs/heads/master@{#459685}
Committed: https://chromium.googlesource.com/chromium/src/+/d0fef1556f8a954735cb20f8d90d5b59dba32458

[imcheng, 2017-03-27 22:43:54]

Description was changed from

==========
[Media Router] Make MRUIService dispose its dependencies on MRMojoImpl in
Shutdown()

Both MediaRouterUIService and MediaRouterMojoImpl are KeyedServices, and the
dependency from the former to the latter should be disposed in its Shutdown()
method. |action_controller_| is an observer to MediaRouterMojoImpl, so it needs
to be reset in Shutdown().

BUG=705216

Review-Url: https://codereview.chromium.org/2774383003
Cr-Commit-Position: refs/heads/master@{#459900}
(cherry picked from commit 6812c7313dd67fcfad6f95d4b5a91cf7dcfda06a)
==========

to

==========
[Media Router] Make MRUIService dispose its dependencies on MRMojoImpl in
Shutdown()

Both MediaRouterUIService and MediaRouterMojoImpl are KeyedServices, and the
dependency from the former to the latter should be disposed in its Shutdown()
method. |action_controller_| is an observer to MediaRouterMojoImpl, so it needs
to be reset in Shutdown().

BUG=705216

Review-Url: https://codereview.chromium.org/2774383003
Cr-Commit-Position: refs/heads/master@{#459900}
(cherry picked from commit 6812c7313dd67fcfad6f95d4b5a91cf7dcfda06a)

Review-Url: https://codereview.chromium.org/2772343004 .
Cr-Commit-Position: refs/branch-heads/3053@{#3}
Cr-Branched-From:
bba05f44fe583ffa69c22d36f91aaebe0ceea282-refs/heads/master@{#459685}
Committed:
https://chromium.googlesource.com/chromium/src/+/d0fef1556f8a954735cb20f8d90d...
==========

[imcheng, 2017-03-27 22:43:55]

Committed patchset #1 (id:1) manually as
d0fef1556f8a954735cb20f8d90d5b59dba32458.