DevTools: Hide the overrides notice for the time the view size is displayed upon resize

The overrides notice overlaps the view size label, which is displayed for a brief
period after a browser window resize. We should just temporarily hide the overrides notice.

R=pfeldman, vsevik, yurys@chromium.org
BUG=265834

Review URL: https://chromiumcodereview.appspot.com/21130009

git-svn-id: svn://svn.chromium.org/blink/trunk@155240 bbb929c8-8fbe-4397-9dbb-9b2b20218538