GitLab

When S13nServiceWorker is enabled these tests requre an instance
of URLLoaderFactory. Add a mock URLLoaderFactory and set them in
tests. This makes tests pass.

Bug: 860361
Change-Id: I2cfa371c1c1076d895398686b3df36340664e30b
Reviewed-on: https://chromium-review.googlesource.com/1152337Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579243}