Revert of Collect data reduction proxy UMA on all platforms

Revert of Collect data reduction proxy UMA on all platforms (https://codereview.chromium.org/266033002/)

Reason for revert:
Causes a sizes regression, starting in http://build.chromium.org/p/chromium/builders/Linux%20x64/builds/64712

+# data_reduction_proxy_settings.cc data_reduction_proxy::DataReductionProxySettings::key_
+# data_reduction_proxy_settings.cc __cxa_atexit@plt [registers a dtor to run at exit]
+# data_reduction_proxy_settings.cc __init_array_end+0x3868
+# data_reduction_proxy_settings.cc __init_array_end+0x3b88
+# data_reduction_proxy_settings.cc __init_array_end+0x530

Original issue's description:
> Collect data reduction proxy UMA on all platforms
> 
> UMA for the data reduction proxy was gated behind preprocessor
> directives that resticted the logic to Android and iOS. This
> change opens UMA calculations and collection up to all platforms.
> 
> BUG=369619
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=269026

TBR=mef@chromium.org,marq@chromium.org,bengr@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=369619
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=269041

[tapted, 2014-05-08 05:57:19]

Created Revert of Collect data reduction proxy UMA on all platforms

[tapted, 2014-05-08 05:57:52]

The CQ bit was unchecked by tapted@chromium.org

[tapted, 2014-05-08 06:00:20]

The CQ bit was checked by tapted@chromium.org

[commit-bot: I haz the power, 2014-05-08 06:02:39]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tapted@chromium.org/274453011/1

[commit-bot: I haz the power, 2014-05-08 06:05:36]

Change committed as 269041