This allows to avoid passing around Isolate instance for no actual reason when
generating "codegen" functions.

Bug: v8:8015
Change-Id: Ic3a9bd5a8ecb5b559479e44c5e1309a78a1546e7
Reviewed-on: https://chromium-review.googlesource.com/1226133Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55926}