Revert of Implement flag and source getters on RegExp.prototype. (patchset #3 id:50001 of https://codereview.chromium.org/1419823010/ )

Reason for revert:
Performance issue.

Original issue's description:
> Implement flag and source getters on RegExp.prototype.
>
> R=littledan@chromium.org
> BUG=v8:3715, v8:4528
> LOG=Y
>
> Committed: https://crrev.com/60e8877e161fe6175e19fafce2d6ed1c3999cdb1
> Cr-Commit-Position: refs/heads/master@{#31753}
>
> Committed: https://crrev.com/b5c80a31ad266eb38a0cf2ff756be59c66d34aa5
> Cr-Commit-Position: refs/heads/master@{#31773}

TBR=littledan@chromium.org,jochen@chromium.org,ulan@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:3715, v8:4528

Review URL: https://codereview.chromium.org/1409013006

Cr-Commit-Position: refs/heads/master@{#31780}