Draw the same portion of the frame background behind the tabstrip in maximized
mode as in restored mode.

Themes which tried to align the tab and frame images couldn't do so in both
maximized and restored modes, since the alignment changed; so they had to pick
one.  This makes the alignment the same in both modes so that themes which
looked correct in restored mode will now look correct in maximized mode as well.

The other way to fix this -- make restored mode match maximized mode -- isn't
possible, as that would put the top of the frame background image in the middle
of the top section of the frame in restored windows, leaving nothing above it.
This also means that for themes which chose to look correct in maximized mode
and wrong in restored mode, they'll now look wrong all the time :(.

TEST=Apply the "Dots" theme from the webstore.  The alignment of the tab and new tab button images against the frame background should be the same in maximized mode as in restored mode.

Review URL: https://codereview.chromium.org/1412833008 .

Cr-Commit-Position: refs/heads/master@{#358512}
14 files changed