Remove SafeBrowsing LightSpeed experiment code.

Remove SafeBrowsing LightSpeed experiment code.

The experiment is now concluded.

BUG=450037
Committed: https://crrev.com/5bef655c3a9bed25ff2bb87584effebd2940268a
Cr-Commit-Position: refs/heads/master@{#329159}

[Alexei Svitkine (slow), 2015-05-08 20:14:01]

asvitkine@chromium.org changed reviewers:
+ mattm@chromium.org

[mattm, 2015-05-08 22:15:50]

lgtm

[Alexei Svitkine (slow), 2015-05-08 22:18:17]

The CQ bit was checked by asvitkine@chromium.org

[commit-bot: I haz the power, 2015-05-08 22:23:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1126233005/1

[commit-bot: I haz the power, 2015-05-09 00:03:55]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-05-09 00:03:57]

Try jobs failed on following builders:
  linux_chromium_compile_dbg_32_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[Alexei Svitkine (slow), 2015-05-11 15:41:09]

The CQ bit was checked by asvitkine@chromium.org

[Alexei Svitkine (slow), 2015-05-11 15:41:10]

The patchset sent to the CQ was uploaded after l-g-t-m from mattm@chromium.org
Link to the patchset: https://codereview.chromium.org/1126233005/#ps20001
(title: "Add field_trial.h include.")

[commit-bot: I haz the power, 2015-05-11 15:42:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1126233005/20001

[commit-bot: I haz the power, 2015-05-11 16:46:36]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-11 16:47:38]

Patchset 2 (id:??) landed as
https://crrev.com/5bef655c3a9bed25ff2bb87584effebd2940268a
Cr-Commit-Position: refs/heads/master@{#329159}