[Mac] Fix regression where commands were disabled in full screen.

[Mac] Fix regression where commands were disabled in full screen.

This was caused by: https://codereview.chromium.org/1250403002

That CL moved where command validation happened, but the new
handler wasn't hooked up to the full screen window that gets
opened on 10.6.

Note: The 10.6 behavior can be simulated by changing the
return value of SupportsSystemFullscreen() to false.

BUG=569418
TEST=On Mac OS 10.6, check that cmd-shift-F can toggle full
screen back and forth.

Review URL: https://codereview.chromium.org/1520283003

Cr-Commit-Position: refs/heads/master@{#365375}
(cherry picked from commit 4d1e70c750dc009ce1c23e76b8c2009264dba0ef)

Committed: https://chromium.googlesource.com/chromium/src/+/38b1a83423628993396862e4a843d1062c1f291a

[Alexei Svitkine (slow), 2015-12-17 16:15:43]

Description was changed from

==========
[Mac] Fix regression where commands were disabled in full screen.

This was caused by: https://codereview.chromium.org/1250403002

That CL moved where command validation happened, but the new
handler wasn't hooked up to the full screen window that gets
opened on 10.6.

Note: The 10.6 behavior can be simulated by changing the
return value of SupportsSystemFullscreen() to false.

BUG=569418
TEST=On Mac OS 10.6, check that cmd-shift-F can toggle full
screen back and forth.

Review URL: https://codereview.chromium.org/1520283003

Cr-Commit-Position: refs/heads/master@{#365375}
(cherry picked from commit 4d1e70c750dc009ce1c23e76b8c2009264dba0ef)
==========

to

==========
[Mac] Fix regression where commands were disabled in full screen.

This was caused by: https://codereview.chromium.org/1250403002

That CL moved where command validation happened, but the new
handler wasn't hooked up to the full screen window that gets
opened on 10.6.

Note: The 10.6 behavior can be simulated by changing the
return value of SupportsSystemFullscreen() to false.

BUG=569418
TEST=On Mac OS 10.6, check that cmd-shift-F can toggle full
screen back and forth.

Review URL: https://codereview.chromium.org/1520283003

Cr-Commit-Position: refs/heads/master@{#365375}
(cherry picked from commit 4d1e70c750dc009ce1c23e76b8c2009264dba0ef)

Committed:
https://chromium.googlesource.com/chromium/src/+/38b1a83423628993396862e4a843...
==========

[Alexei Svitkine (slow), 2015-12-17 16:15:44]

Committed patchset #1 (id:1) manually as
38b1a83423628993396862e4a843d1062c1f291a.