Chrome OS: Fix window header animation for overview mode.

Before this change, there was a flash of white above every non-browser
window when entering overview mode, because the overview code was using
the kTopViewColor property to get the frame's color. That property was
only set correctly for certain browser windows (not, e.g., v1 apps)
and for some others it was set to always use the inactive frame color.

Instead, use kFrame{Active,Inactive}ColorKey which should be set for all
windows and also has a reasonable default.

Related to linked bug because it reduces the number of differences
between ash and classic browser windows.

Bug: 854704
Change-Id: Ie86223cb97509f860069895fefa1054b48080ed9
Reviewed-on: https://chromium-review.googlesource.com/1119356
Commit-Queue: Evan Stade <estade@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575714}
8 files changed