The Uint32(limit) conversion can end up transitioning the regexp
instance to slow mode. In this case we need to bail out to runtime while
ensuring that ToUint32 is not observably called a second time. We do
this by passing the already-converted value to runtime.

This particular path was broken and we ended up passing the original
maybe_limit value to runtime instead.

TBR=yangguo@chromium.org

Bug: chromium:758763
Change-Id: If7f23b452d2e134ad9be3d4ef1d78d1c946fcef0
Reviewed-on: https://chromium-review.googlesource.com/635588Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47609}