Stop using default_factory for AppCache and reduce RBPI::CreateDefaultURLLoaderFactoryBundle usage

* Stop using URLLoaderFactoryBundle::default_factory for AppCache,
  this over-generalization has been causing a lot of confusions.
* Deprecate URLLoaderFactoryBundle::default_network_factory, which is
  no longer needed after removing the default_factory == AppCache hack.
* This change also allows us to remove more RendererBlinkPlatformImpl::
  CreateDefaultURLLoaderFactoryBundle callsites for most of
  NetworkService-enabled cases, which was needed only when
  default_factory was dropped (just to skip AppCache, which is no
  longer needed), or for initial empty document cases (this is
  still needed).

Bug: 891872
Change-Id: I9b58097430b76d96d96864043b63553e88e3066c
Reviewed-on: https://chromium-review.googlesource.com/c/1371310
Commit-Queue: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Ɓukasz Anforowicz <lukasza@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#616269}(cherry picked from commit 9f2cede3f8cdd694c865fc394a9af3edc672b10d)
Reviewed-on: https://chromium-review.googlesource.com/c/1474539
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/branch-heads/3626@{#873}
Cr-Branched-From: d897fb137fbaaa9355c0c93124cc048824eb1e65-refs/heads/master@{#612437}
18 files changed