RegExpSubclassExecJS and RegExpExecJS only differed in the additional
TO_BOOLEAN on global and sticky flags and the useless (i < 0) check.

R=littledan@chromium.org
BUG=v8:5339

Review-Url: https://codereview.chromium.org/2337923002
Cr-Commit-Position: refs/heads/master@{#39417}