Remove unused data reduction proxy prefs from direct settings API.

Remove unused data reduction proxy prefs from direct settings API.

Also remove unused data reduction pref from preferences API.

BUG=442494
Committed: https://crrev.com/e8280f3afe7cff09bb5b23c959928ccbdc16da25
Cr-Commit-Position: refs/heads/master@{#329263}

[Not at Google. Contact bengr, 2015-05-06 18:34:23]

kundaji@chromium.org changed reviewers:
+ kalman@chromium.org

[Not at Google. Contact bengr, 2015-05-06 18:43:45]

kalman:
  chrome/browser/extensions/api/preference/chrome_direct_setting_api.cc
  chrome/browser/extensions/api/preference/preference_api.cc
  chrome/common/extensions/api/data_reduction_proxy.json
  chrome/common/extensions/api/preferences_private.json

[Not at Google. Contact bengr, 2015-05-11 16:18:05]

Ping. Ben, Can you please take a look?

[not at google - send to devlin, 2015-05-11 16:23:37]

lgtm, sorry I missed this.

[Not at Google. Contact bengr, 2015-05-11 22:00:28]

The CQ bit was checked by kundaji@chromium.org

[Not at Google. Contact bengr, 2015-05-11 22:00:29]

The patchset sent to the CQ was uploaded after l-g-t-m from kalman@chromium.org
Link to the patchset: https://codereview.chromium.org/1130863002/#ps20001
(title: "Sync to head")

[commit-bot: I haz the power, 2015-05-11 22:02:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1130863002/20001

[commit-bot: I haz the power, 2015-05-11 22:54:03]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-11 22:55:34]

Patchset 2 (id:??) landed as
https://crrev.com/e8280f3afe7cff09bb5b23c959928ccbdc16da25
Cr-Commit-Position: refs/heads/master@{#329263}