In a recent CL I introduced module-level CodeSpaceMemoryModificationScopes,
which means that the number of CodeSpaceMemoryModificationScopes which
are opened aside from TurboFan compilation is not linear in the number
of functions anymore. In that CL, however, I did not remove scopes which
became obsolete. This CL removes now these obsolete scopes, and
introduces some scopes where shared code was used from outside the
compilation logic.

R=mstarzinger@chromium.org, clemensh@chromium.org

Bug: chromium:787731
Change-Id: I37d514efa3a4b10adb7008986a9c91e4557ce618
Reviewed-on: https://chromium-review.googlesource.com/790490
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49662}