Revert of Rename String.prototype.contains to 'includes'.

Revert of Rename String.prototype.contains to 'includes'. (patchset #1 id:1 of https://codereview.chromium.org/742963002/)

Reason for revert:
Breaks test262-es6:
http://build.chromium.org/p/client.v8/builders/V8%20Linux/builds/1289

Original issue's description:
> Rename String.prototype.contains to 'includes'.
> 
> Per TC39 Nov 2014 decison.
> 
> R=arv@chromium.org,yangguo@chromium.org
> LOG=Y
> 
> Committed: https://chromium.googlesource.com/v8/v8/+/b5379216e23ff0ec734e70361dd07057c2421c96

TBR=arv@chromium.org,yangguo@chromium.org,dslomov@chromium.org
NOTREECHECKS=true
NOTRY=true

Committed: https://chromium.googlesource.com/v8/v8/+/cdc6e159bab8bee5d8b084bf0e370873d0968a38

[Michael Achenbach, 2014-11-20 09:03:05]

Created Revert of Rename String.prototype.contains to 'includes'.

[commit-bot: I haz the power, 2014-11-20 09:03:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/745543002/1

[commit-bot: I haz the power, 2014-11-20 09:03:51]

Committed patchset #1 (id:1)

[Yang, 2014-11-20 09:04:12]

On 2014/11/20 09:03:05, Michael Achenbach wrote:
> Created Revert of Rename String.prototype.contains to 'includes'.

LGTM. test262-es6.status needs to be updated before relanding.

[mathias, 2014-11-20 09:55:49]

On 2014/11/20 09:04:12, Yang wrote:
> On 2014/11/20 09:03:05, Michael Achenbach wrote:
> > Created Revert of Rename String.prototype.contains to 'includes'.
> 
> LGTM. test262-es6.status needs to be updated before relanding.

test262 patch: https://github.com/tc39/test262/pull/119