Remove long gone Windows side of the BackgroundRendererProcesses experiment.

Remove long gone Windows side of the BackgroundRendererProcesses experiment.

All the code for it was removed long ago, this code was kept for the Mac
side of the experiment (but I forgot to remove the OS_WIN ifdef so this code
was kept when recently removing the Mac side of the experiment in r350611).

BUG=458594
Committed: https://crrev.com/b48a93f3b903adcaf58da7837cfd10d68bd20bcb
Cr-Commit-Position: refs/heads/master@{#351792}

[gab, 2015-09-29 16:34:43]

gab@chromium.org changed reviewers:
+ avi@chromium.org

[gab, 2015-09-29 16:34:55]

Avi PTAL.

Thanks,
Gab

[Avi (use Gerrit), 2015-09-29 16:37:04]

The CQ bit was checked by avi@chromium.org

[Avi (use Gerrit), 2015-09-29 16:37:04]

lgtm

[commit-bot: I haz the power, 2015-09-29 16:37:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1377893002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1377893002/1

[gab, 2015-10-01 13:25:24]

The CQ bit was checked by gab@chromium.org

[gab, 2015-10-01 13:25:24]

The patchset sent to the CQ was uploaded after l-g-t-m from avi@chromium.org
Link to the patchset: https://codereview.chromium.org/1377893002/#ps20001
(title: "rm string_util.h -- last usage was removed StartsWith call")

[commit-bot: I haz the power, 2015-10-01 13:25:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1377893002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1377893002/20001

[commit-bot: I haz the power, 2015-10-01 14:09:13]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-10-01 14:10:04]

Patchset 2 (id:??) landed as
https://crrev.com/b48a93f3b903adcaf58da7837cfd10d68bd20bcb
Cr-Commit-Position: refs/heads/master@{#351792}