Adding back stale previews functionality

This was unintentionally removed, and needs to be added back. In the
future, this might move to DataReductionProxyData.

Bug: 813948
Change-Id: Iee0b5c16fc99860a9682804d1948651b434ab7ea
Reviewed-on: https://chromium-review.googlesource.com/927749
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#538847}(cherry picked from commit 97ba93d3e446d69e3b4311d604e1c027eacf84e9)
Reviewed-on: https://chromium-review.googlesource.com/939651
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Cr-Commit-Position: refs/branch-heads/3325@{#611}
Cr-Branched-From: bc084a8b5afa3744a74927344e304c02ae54189f-refs/heads/master@{#530369}
1 file changed