Fix remaining references to the old LayoutTests/w3c directories.

TBR=jianli@chromium.org
BUG=413454

Review URL: https://codereview.chromium.org/544173005

git-svn-id: svn://svn.chromium.org/blink/trunk@181928 bbb929c8-8fbe-4397-9dbb-9b2b20218538