GitLab

A client may set custom WindowStateDelegate, so the code should be
in the CustomFrameViewAsh.

BUG=33693796
TEST=covered by unit tests.

Change-Id: Iccacddf8a0bce01ed1a3819c959e73d591a8d8ef
Reviewed-on: https://chromium-review.googlesource.com/972677
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Tao Wu <wutao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545092}