I think this can just use existing LoadFlags already set on URLRequests.  If bypass_cache or validate_cache is set, bypass offline page.

Thanks. I was thinking the same thing: https://codereview.chromium.org/2563493002/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bc5da354fd37ccda92436a438f3f41ff0d1b940e

commit bc5da354fd37ccda92436a438f3f41ff0d1b940e
Author: ryansturm <ryansturm@chromium.org>
Date: Wed Dec 14 18:43:03 2016

Disallow showing offline previews on a reload.

This change prevents reloads being shown an offline preview. This does
not prevent other previews from being shown. A reload on an offline
preview is still considered to be non-opt out for the blacklist unless the user hit "show original".

BUG= 672237 

Review-Url: https://codereview.chromium.org/2563493002
Cr-Commit-Position: refs/heads/master@{#438549}

[modify] https://crrev.com/bc5da354fd37ccda92436a438f3f41ff0d1b940e/components/previews/core/previews_black_list.h
[modify] https://crrev.com/bc5da354fd37ccda92436a438f3f41ff0d1b940e/components/previews/core/previews_io_data.cc
[modify] https://crrev.com/bc5da354fd37ccda92436a438f3f41ff0d1b940e/components/previews/core/previews_io_data_unittest.cc
[modify] https://crrev.com/bc5da354fd37ccda92436a438f3f41ff0d1b940e/tools/metrics/histograms/histograms.xml