Revert of Implement flag and source getters on RegExp.prototype. (patchset #6 id:110001 of https://codereview.chromium.org/1419823010/ )

Reason for revert:
browser_tests failure with --gtest_filter=ExternallyConnectableMessagingTest.EnablingAndDisabling

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}
>
> Committed: https://crrev.com/85494e90bb63a3a9e19a1bf862cb6bfcb0162ee9
> Cr-Commit-Position: refs/heads/master@{#31782}
>
> Committed: https://crrev.com/152163c1646b45f5fc5d31a4ec2eb55d7f4a2ffc
> Cr-Commit-Position: refs/heads/master@{#31804}

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/1426413002

Cr-Commit-Position: refs/heads/master@{#31818}