Make the video layer visibility configurable in OverlayFullscreenVideo mode

Make the video layer visibility configurable in OverlayFullscreenVideo mode

OverlayFullscreenVideo initially always hid the video GraphicsLayer, but
that was changed to always show it in http://crrev.com/1907753002.
That approach doesn't work when the media player is WebMediaPlayerAndroid
and the video has a background image because it made the background visible.

This CL reverts that change to do it a better way: now the WebMediaPlayer
can choose whether the video layer is hidden. So WMPA can hide it as it
always has, and WMPI can make it visible.

TEST=LayoutTests
BUG=615245, 603521

[watk, 2016-06-21 21:45:00]

watk@chromium.org changed reviewers:
+ chrishtr@chromium.org, qinmin@chromium.org

[watk, 2016-06-21 21:45:01]

Hey chrishtr, PTAL at the blink changes.

qinmin@, PTAL at WMPA. The changes are pretty much just to revert it to how it
was before my last CL.

[watk, 2016-06-21 21:45:31]

Description was changed from

==========
Make the video layer visibility configurable in OverlayFullscreenVideo mode

OverlayFullscreenVideo initially always hid the video GraphicsLayer, but
that was changed to always show it in http://crrev.com/1907753002.
That approach doesn't work when the media player is WebMediaPlayerAndroid
and the video has a background image because it made the background visible.

This CL reverts that change to do it a better way: now the WebMediaPlayer
can choose whether the video layer is hidden. So WMPA can hide it as it
always has, and WMPI can make it visible.

BUG=603521
==========

to

==========
Make the video layer visibility configurable in OverlayFullscreenVideo mode

OverlayFullscreenVideo initially always hid the video GraphicsLayer, but
that was changed to always show it in http://crrev.com/1907753002.
That approach doesn't work when the media player is WebMediaPlayerAndroid
and the video has a background image because it made the background visible.

This CL reverts that change to do it a better way: now the WebMediaPlayer
can choose whether the video layer is hidden. So WMPA can hide it as it
always has, and WMPI can make it visible.

TEST=LayoutTests
BUG=615245,603521
==========

[watk, 2016-06-21 21:54:32]

Note: I will need to merge this back to M52 to fix the regression with WMPA when
the video has a background image (615245).

[watk, 2016-06-22 00:29:27]

qinmin@, you can disregard this for now. Working on a different fix suggested by
chrishtr@.