Prevent X11 clients from changing the size of windows in some cases.

Limit when client can change window size to when not maximized/fullscreen
or when the compositor is not resizing the window.

Bug: 825463
Change-Id: Ia52c688a69ac39bf964ad15e84938dd99188e541
Reviewed-on: https://chromium-review.googlesource.com/986263
Reviewed-by: David Reveman <reveman@chromium.org>
Tested-by: David Reveman <reveman@chromium.org>