Media Controls: don't activate buttons when tapping on hidden controls.

Media Controls: don't activate buttons when tapping on hidden controls.

This should also fix an accessibility issue where activating the
controls while hidden would randomly activate one of the buttons.

BUG=654648, 652698
Review-Url: https://chromiumcodereview.appspot.com/2431583004
Cr-Commit-Position: refs/heads/master@{#426452}
(cherry picked from commit cb55961999ccce51568d3fcdfbb51c8ba5bcfdb2)

Committed: https://chromium.googlesource.com/chromium/src/+/20108d0c66bf5aa78246c7d18b9cf1e57adb81e7

[mlamouri (slow - plz ping), 2016-10-25 12:40:12]

Description was changed from

==========
Media Controls: don't activate buttons when tapping on hidden controls.

This should also fix an accessibility issue where activating the
controls while hidden would randomly activate one of the buttons.

BUG=654648,652698

Review-Url: https://chromiumcodereview.appspot.com/2431583004
Cr-Commit-Position: refs/heads/master@{#426452}
(cherry picked from commit cb55961999ccce51568d3fcdfbb51c8ba5bcfdb2)
==========

to

==========
Media Controls: don't activate buttons when tapping on hidden controls.

This should also fix an accessibility issue where activating the
controls while hidden would randomly activate one of the buttons.

BUG=654648,652698

Review-Url: https://chromiumcodereview.appspot.com/2431583004
Cr-Commit-Position: refs/heads/master@{#426452}
(cherry picked from commit cb55961999ccce51568d3fcdfbb51c8ba5bcfdb2)

Committed:
https://chromium.googlesource.com/chromium/src/+/20108d0c66bf5aa78246c7d18b9c...
==========

[mlamouri (slow - plz ping), 2016-10-25 12:40:14]

Committed patchset #1 (id:1) manually as
20108d0c66bf5aa78246c7d18b9cf1e57adb81e7.