Skip overflow adjustment checks when possible in StyleAdjuster

Continuing the work to make StyleAdjuster cheaper we can skip all the work
related to overflow adjustment in the common case when overflow is visible.

Review URL: https://codereview.chromium.org/214413011

git-svn-id: svn://svn.chromium.org/blink/trunk@170306 bbb929c8-8fbe-4397-9dbb-9b2b20218538