Remove stray forward declaration of WebThread.

Bug: 826203
Change-Id: I0d8a2ad46df93e3bf50b71a34b4abb315844a84e
Reviewed-on: https://chromium-review.googlesource.com/1250522
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Commit-Queue: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595064}
1 file changed