Move the shadows out of paintTextWithShadows.

It unnecessarily entangles one aspect of style with the actual text painting.

Also rename it paintText since it no longer deals with shadows.

Review URL: https://codereview.chromium.org/472083002

git-svn-id: svn://svn.chromium.org/blink/trunk@180741 bbb929c8-8fbe-4397-9dbb-9b2b20218538