[Mac] Remove special hack for incognito NTP background color

It's not required anymore after https://crrev.com/c/840028. (It had also
diverged from the correct color in the meantime...)

Bug: 21798, 719236
Change-Id: If98185ffe59865dcf7fb52b8d5a3ed534db60aed
Reviewed-on: https://chromium-review.googlesource.com/859760
Commit-Queue: Yuri Wiitala <miu@chromium.org>
Reviewed-by: ccameron <ccameron@chromium.org>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#530077}
1 file changed