S13nSW: Use URLLoaderFactory that directly goes to network for SWSubresourceLoader

Instead of using a bundled URLLoaderFactory that can selectively get
multiple factories. The bundled URLLoader factory's default factory
for network (e.g. for http/https) scheme may be replaced with custom
factories (e.g. AppCache one), and SW doesn't want to use it when
falling back.

We used to use 'constraints' flag in SharedURLLoaderFactory to control
this behavior but it's needed only one place where Worker makes
SW-controled fetch. Instead we can just pass the network-direct URLLoader
factory in addition to the bundled one, then we can eliminate the
'constraints' flag too.

R=falken@chromium.org, jam@chromium.org

Bug: 715640
Change-Id: I1604de28b22c95e0fd79aa230c5f0cb1c59edc85
Reviewed-on: https://chromium-review.googlesource.com/923621
Commit-Queue: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537271}
6 files changed