Remove deprecated web_task_runner.h.

It's unused as of now.

Bug: 826203
Change-Id: I8e54a8234cb83c1ac871768a62fb2224be9ba0d0
Reviewed-on: https://chromium-review.googlesource.com/c/1356461
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Commit-Queue: Yuta Kitamura <yutak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612591}
2 files changed