Land test case for RegExp.source.
Land test case for RegExp.source.

BUG=chromium:447561
LOG=N
TBR=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/878033003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#26297}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh