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This CL plumbs an URLLoader Factory (and other related information)
from navigation url loader impl to Previews URLLoader during creation.
This allows Previews URLLoader to create an underlying network service
URLLoader for fetching a lite page preview. This adds URLLoaderClient
handling for the serving loader, and allows both URLLoaders to actually
handle URLLoaderRequests instead of always falling back.

This is the minimal CL to be able to attempt server HTTPS lite page
previews. Browser tests will be turned on as more behavior is supported.

Bug: 921740
Change-Id: I8993d00d76c1013eb08b06c544f1c1a491a11da1
Reviewed-on: https://chromium-review.googlesource.com/c/1434521
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Reviewed-by: Camille Lamy <clamy@chromium.org>
Reviewed-by: Martin Šrámek <msramek@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632761}