[Media>UI] Reset media session actions when navigating away

[Media>UI] Reset media session actions when navigating away

There is a bug caused by media session actions being not properly reset
when navigating away, so that the notification control buttons stays the
same when the new page starts to play media. This CL fixes the issue.

BUG=689664
Review-Url: https://codereview.chromium.org/2680103002
Cr-Commit-Position: refs/heads/master@{#449032}
(cherry picked from commit e9c5df7d3be68ce0d8cf656dac0b9a1912ea5a28)

Review-Url: https://codereview.chromium.org/2685943002 .
Cr-Commit-Position: refs/branch-heads/2987@{#389}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/15ab0ba733d50b9f7567bd77049aafeaa9114b0b

[Zhiqiang Zhang (Slow), 2017-02-08 18:25:16]

Description was changed from

==========
[Media>UI] Reset media session actions when navigating away

There is a bug caused by media session actions being not properly reset
when navigating away, so that the notification control buttons stays the
same when the new page starts to play media. This CL fixes the issue.

BUG=689664

Review-Url: https://codereview.chromium.org/2680103002
Cr-Commit-Position: refs/heads/master@{#449032}
(cherry picked from commit e9c5df7d3be68ce0d8cf656dac0b9a1912ea5a28)
==========

to

==========
[Media>UI] Reset media session actions when navigating away

There is a bug caused by media session actions being not properly reset
when navigating away, so that the notification control buttons stays the
same when the new page starts to play media. This CL fixes the issue.

BUG=689664

Review-Url: https://codereview.chromium.org/2680103002
Cr-Commit-Position: refs/heads/master@{#449032}
(cherry picked from commit e9c5df7d3be68ce0d8cf656dac0b9a1912ea5a28)

Review-Url: https://codereview.chromium.org/2685943002 .
Cr-Commit-Position: refs/branch-heads/2987@{#389}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/15ab0ba733d50b9f7567bd77049a...
==========

[Zhiqiang Zhang (Slow), 2017-02-08 18:25:17]

Committed patchset #1 (id:1) manually as
15ab0ba733d50b9f7567bd77049aafeaa9114b0b.