[Media>UI] Fix a media notification update issue when audio focus changes between tabs

[Media>UI] Fix a media notification update issue when audio focus changes between tabs

There's a issue which is caused by the asynchronousness of audio focus.
When tab B gains focus from tab A, we will first receive the event that
A becomes playing, and then B becomes paused. We should ignore the
notification updates when the tab id mismatches the current notification
and the tab is paused.

BUG=695967
Review-Url: https://codereview.chromium.org/2714993002
Cr-Commit-Position: refs/heads/master@{#453206}
(cherry picked from commit 1ee77687069628ebd0bba3ff791a5ee6c8d17b41)

Review-Url: https://codereview.chromium.org/2717293003 .
Cr-Commit-Position: refs/branch-heads/2987@{#695}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/5dfc4b56d28e35a36a63c77bad993850f966a3fd

[Zhiqiang Zhang (Slow), 2017-02-27 14:54:39]

Description was changed from

==========
[Media>UI] Fix a media notification update issue when audio focus changes
between tabs

There's a issue which is caused by the asynchronousness of audio focus.
When tab B gains focus from tab A, we will first receive the event that
A becomes playing, and then B becomes paused. We should ignore the
notification updates when the tab id mismatches the current notification
and the tab is paused.

BUG=695967

Review-Url: https://codereview.chromium.org/2714993002
Cr-Commit-Position: refs/heads/master@{#453206}
(cherry picked from commit 1ee77687069628ebd0bba3ff791a5ee6c8d17b41)
==========

to

==========
[Media>UI] Fix a media notification update issue when audio focus changes
between tabs

There's a issue which is caused by the asynchronousness of audio focus.
When tab B gains focus from tab A, we will first receive the event that
A becomes playing, and then B becomes paused. We should ignore the
notification updates when the tab id mismatches the current notification
and the tab is paused.

BUG=695967

Review-Url: https://codereview.chromium.org/2714993002
Cr-Commit-Position: refs/heads/master@{#453206}
(cherry picked from commit 1ee77687069628ebd0bba3ff791a5ee6c8d17b41)

Review-Url: https://codereview.chromium.org/2717293003 .
Cr-Commit-Position: refs/branch-heads/2987@{#695}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/5dfc4b56d28e35a36a63c77bad99...
==========

[Zhiqiang Zhang (Slow), 2017-02-27 14:54:40]

Committed patchset #1 (id:1) manually as
5dfc4b56d28e35a36a63c77bad993850f966a3fd.