Ensure to add FrameCenterButton to HeaderView

It turns out, depending on the timing, UpdateCenterButton() is not
triggered after the button is set because it's supposed to be
called when the caption button mask is set in exo, but in the case
of the center button, instantiating the button can be delayed
as it requires app id to be set. So UpdateCenterButton needs to be
explicitly called.

Ideally, we want FrameView to call the function, but as it requres
some amout of work to refactor, let's just call it from the client
for now.

This CL also does some cleanup of removing the shell surface from
UpdateCompatModeButton() as we've determined not to put maximized
apps into compat mode.

BUG=b:191435012
TEST=tast run DUT arc.ResizeLock

Change-Id: Ic16e8d4b33ba2364109b6ac5a513eb0051f7e0bc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2971678
Commit-Queue: Kazuki Takise <takise@chromium.org>
Auto-Submit: Kazuki Takise <takise@chromium.org>
Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Cr-Commit-Position: refs/heads/master@{#893744}