Remove stub WebThemeEngine headers, DEPS files for includes.

R=jamesr@chromium.org
BUG=327471

Review URL: https://codereview.chromium.org/154793003

git-svn-id: svn://svn.chromium.org/blink/trunk@167145 bbb929c8-8fbe-4397-9dbb-9b2b20218538