Remove unused RegExp private symbols.

Remove unused RegExp private symbols.

R=ulan@chromium.org

Committed: https://crrev.com/6e981a32a68df5f5c176c5c5045c6cecdd8b0a31
Cr-Commit-Position: refs/heads/master@{#31861}

[Yang, 2015-11-05 06:45:37]

The CQ bit was checked by yangguo@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-11-05 06:45:41]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1408003012/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1408003012/1

[commit-bot: I haz the power, 2015-11-05 07:22:39]

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

[commit-bot: I haz the power, 2015-11-05 07:22:40]

Dry run: This issue passed the CQ dry run.

[ulan, 2015-11-06 14:38:38]

lgtm

[Yang, 2015-11-06 14:43:11]

The CQ bit was checked by yangguo@chromium.org

[commit-bot: I haz the power, 2015-11-06 14:43:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1408003012/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1408003012/1

[commit-bot: I haz the power, 2015-11-06 15:24:40]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-06 15:25:28]

Patchset 1 (id:??) landed as
https://crrev.com/6e981a32a68df5f5c176c5c5045c6cecdd8b0a31
Cr-Commit-Position: refs/heads/master@{#31861}