[Video] Reset new processed frame callback on the compositor thread.

[Video] Reset new processed frame callback on the compositor thread.

The callback is set and used on the compositor thread but is reset on the
media thread, causing a data race.
Moved resetting the callback to the OnRenderingStateChange when the state is
set to false.

BUG=684458
TEST=manual

Review-Url: https://codereview.chromium.org/2651323002
Cr-Commit-Position: refs/heads/master@{#446515}
(cherry picked from commit b5c8d0d1bed4056880ad70ed949714f9edc0f81b)

Review-Url: https://codereview.chromium.org/2660993002 .
Cr-Commit-Position: refs/branch-heads/2987@{#178}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/8249e65739295d3aa951eba40de6221e3b11aae6

[whywhat, 2017-01-30 20:14:59]

Description was changed from

==========
[Video] Reset new processed frame callback on the compositor thread.

The callback is set and used on the compositor thread but is reset on the
media thread, causing a data race.
Moved resetting the callback to the OnRenderingStateChange when the state is
set to false.

BUG=684458
TEST=manual

Review-Url: https://codereview.chromium.org/2651323002
Cr-Commit-Position: refs/heads/master@{#446515}
(cherry picked from commit b5c8d0d1bed4056880ad70ed949714f9edc0f81b)
==========

to

==========
[Video] Reset new processed frame callback on the compositor thread.

The callback is set and used on the compositor thread but is reset on the
media thread, causing a data race.
Moved resetting the callback to the OnRenderingStateChange when the state is
set to false.

BUG=684458
TEST=manual

Review-Url: https://codereview.chromium.org/2651323002
Cr-Commit-Position: refs/heads/master@{#446515}
(cherry picked from commit b5c8d0d1bed4056880ad70ed949714f9edc0f81b)

Review-Url: https://codereview.chromium.org/2660993002 .
Cr-Commit-Position: refs/branch-heads/2987@{#178}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/8249e65739295d3aa951eba40de6...
==========

[whywhat, 2017-01-30 20:15:00]

Committed patchset #1 (id:1) manually as
8249e65739295d3aa951eba40de6221e3b11aae6.