Sets the background color of shelf is opaque black when maximized (2nd)

Sets the background color of shelf is opaque black when maximized (2nd)

Previously the black color was achieved by hiding the desktop background.
Now shelf's background color is opaque black instead.

The first patch (r210763) was reverted due to test failure in win8.

BUG=252422
TEST=covered by the new tests
TBR=jamescook@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=211053

[Jun Mukai, 2013-07-10 19:50:51]

submit with TBR=jamescook because the previous patch was already approved.
The only change from the first one is from GetShelfWidget()->bounds() to
GetShelfLayoutManager()->GetIdealBounds(). This change fixes the test failure in
win8_aura.

[commit-bot: I haz the power, 2013-07-10 19:51:09]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mukai@chromium.org/18637004/9001

[commit-bot: I haz the power, 2013-07-10 19:59:17]

Step "update" is always a major failure.
Look at the try server FAQ for more details.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=android_db...

[commit-bot: I haz the power, 2013-07-10 20:12:41]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mukai@chromium.org/18637004/9001

[commit-bot: I haz the power, 2013-07-11 09:33:03]

Change committed as 211053