Handling HTTPS server Previews URLLoader redirects

This CL adds the functionality of respecting a redirect response from
the lite page server. The redirect is passed through to content and from
that point, navigation continues as normal. This CL also adds a scheme
check to prevent attempts on HTTP (used in Browser tests) until all
extra checks are moved from the navigation throttle code to the
PreviewsState code.

Bug: 921744
Change-Id: I8bb85ae00e3f8ecd2af352a66a6a92f9383668a3
Reviewed-on: https://chromium-review.googlesource.com/c/1460060
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Reviewed-by: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632948}
10 files changed