Ignore MISSING_VIA_HEADER_OTHER bypasses if in relevant finch trial

Ignore MISSING_VIA_HEADER_OTHER bypasses if in relevant finch trial

For clients that are part of the finch trial, change the proxy bypass
logic to not trigger a proxy bypass when a response with a non-4xx
response code is expected to have the data reduction proxy header, but
the data reduction proxy via header is missing.

BUG=413035
Committed: https://crrev.com/dadcc31e94943d59ecef9209e09a557d1594b68a
Cr-Commit-Position: refs/heads/master@{#295825}

[sclittle, 2014-09-19 20:54:19]

sclittle@chromium.org changed reviewers:
+ bengr@chromium.org

[sclittle, 2014-09-19 20:54:36]

bengr: all

Thanks in advance

[bengr, 2014-09-19 21:44:33]

lgtm

[sclittle, 2014-09-19 21:45:58]

The CQ bit was checked by sclittle@chromium.org

[commit-bot: I haz the power, 2014-09-19 21:47:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/583363002/1

[commit-bot: I haz the power, 2014-09-20 00:08:12]

Committed patchset #1 (id:1) as 2d2bbab0e04398b376e932df42b076ccaa1524df

[commit-bot: I haz the power, 2014-09-20 00:08:58]

Patchset 1 (id:??) landed as
https://crrev.com/dadcc31e94943d59ecef9209e09a557d1594b68a
Cr-Commit-Position: refs/heads/master@{#295825}