Cherry-pick "Refactor Regexp.prototype" am: c00e914da2 am: 78139c51eb am: 20093377c7

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/chromium-libpac/+/12135061

Change-Id: Ic6742b4146aadd5bc1a5b6b9de0591a13a038386