service worker: Always use plumbed URLLoaderFactory for subresources

After S13nServiceWorker the browser process always sends a
non-null URLLoaderFactory to renderer process.
ServiceWorkerContextClient doesn't have to use the default
URLLoaderFactory which is supplied from RenderThreadImpl.

This is a preparation for off-the-main-thread service worker
start up.

Change-Id: Idfb44517bc4b5da092c2f90182afe26fa3898e53
Bug: 692909
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1652758
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#669552}
2 files changed