Override the Data Saver API proxy list in DRP integration tests.

Override the Data Saver API proxy list in DRP integration tests.

Use a flag to override the proxy list when using the Data Saver API for
the relevant Data Reduction Proxy integration tests. This should fix the
currently broken fallback_viaheader and http_to_direct_fallback tests.

BUG=526827
Committed: https://crrev.com/386a4d6ab6f234cb64accb303192d840ef28a161
Cr-Commit-Position: refs/heads/master@{#351225}

[sclittle, 2015-09-16 01:47:51]

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

[bustamante, 2015-09-16 18:55:40]

lgtm

Cool, thanks!

[bengr, 2015-09-18 22:42:55]

lgtm

[sclittle, 2015-09-29 00:42:18]

The CQ bit was checked by sclittle@chromium.org

[sclittle, 2015-09-29 00:42:18]

The patchset sent to the CQ was uploaded after l-g-t-m from bengr@chromium.org,
bustamante@chromium.org
Link to the patchset: https://codereview.chromium.org/1350563002/#ps40001
(title: "Rebased")

[commit-bot: I haz the power, 2015-09-29 00:42:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1350563002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1350563002/40001

[commit-bot: I haz the power, 2015-09-29 01:30:09]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-09-29 01:30:58]

Patchset 3 (id:??) landed as
https://crrev.com/386a4d6ab6f234cb64accb303192d840ef28a161
Cr-Commit-Position: refs/heads/master@{#351225}