This inlines the allocation of regexp literals when a boilerplate exists.

Bug: v8:6605,v8:6556
Change-Id: If0f1b9dedf8a7de1ec51c394fe39cf21d2413ac5
Reviewed-on: https://chromium-review.googlesource.com/575240
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46780}