Eagerly escape RegExp.source.

Eagerly escape RegExp.source.

Escaping used to happen lazily, implemented in an accessor property.
However, native implementation of RegExp methods use .source as well.
This leads to performance regressions. Now we do it eagerly instead.

R=jkummerow@chromium.org
BUG=chromium:436447
LOG=N

Committed: https://crrev.com/4a5de9d9e36ff0f8e82ad7f7d48b37d608713b16
Cr-Commit-Position: refs/heads/master@{#27705}

[Jakob Kummerow, 2015-04-09 12:55:29]

lgtm

[Yang, 2015-04-09 12:55:42]

The CQ bit was checked by yangguo@chromium.org

[commit-bot: I haz the power, 2015-04-09 12:55:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1070093002/1

[commit-bot: I haz the power, 2015-04-09 13:22:22]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-09 13:22:36]

Patchset 1 (id:??) landed as
https://crrev.com/4a5de9d9e36ff0f8e82ad7f7d48b37d608713b16
Cr-Commit-Position: refs/heads/master@{#27705}