DCHECK if StoragePartition::GetRequestContext is called with the network service enabled.

There are a few instances remaining which use it, for those use a temporary friend class to disable the DCHECK.

Bug: 837753
Change-Id: I186488d87e44411a131f59b1b0def2133c7e2339
Reviewed-on: https://chromium-review.googlesource.com/c/1355136
Commit-Queue: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613208}
22 files changed