Making offline previews freshness configurable

Making offline previews freshness configurable

This makes the freshness (e.g. the amount of time since download that
the page may be shown as a preview) of offline previews controllable
as a field trial param.

This also sets the default back to 7 days, which was changed during the
offline page refactor that moved the code from the UI thread to the IO
thread.

BUG=669093
Review-Url: https://codereview.chromium.org/2537563002
Cr-Commit-Position: refs/heads/master@{#435251}
(cherry picked from commit e42c5acc8c61a87e6a72352d2428b3f477bd73c1)

Committed: https://chromium.googlesource.com/chromium/src/+/426a071edcb4b14719869f95bd533ea6081c1d0d

[RyanSturm, 2016-12-02 21:15:17]

Description was changed from

==========
Making offline previews freshness configurable

This makes the freshness (e.g. the amount of time since download that
the page may be shown as a preview) of offline previews controllable
as a field trial param.

This also sets the default back to 7 days, which was changed during the
offline page refactor that moved the code from the UI thread to the IO
thread.

BUG=669093

Review-Url: https://codereview.chromium.org/2537563002
Cr-Commit-Position: refs/heads/master@{#435251}
(cherry picked from commit e42c5acc8c61a87e6a72352d2428b3f477bd73c1)
==========

to

==========
Making offline previews freshness configurable

This makes the freshness (e.g. the amount of time since download that
the page may be shown as a preview) of offline previews controllable
as a field trial param.

This also sets the default back to 7 days, which was changed during the
offline page refactor that moved the code from the UI thread to the IO
thread.

BUG=669093

Review-Url: https://codereview.chromium.org/2537563002
Cr-Commit-Position: refs/heads/master@{#435251}
(cherry picked from commit e42c5acc8c61a87e6a72352d2428b3f477bd73c1)

Committed:
https://chromium.googlesource.com/chromium/src/+/426a071edcb4b14719869f95bd53...
==========

[RyanSturm, 2016-12-02 21:15:19]

Committed patchset #1 (id:1) manually as
426a071edcb4b14719869f95bd533ea6081c1d0d.