Port d1b3d426

Original commit message:

    Further refactor the pipeline to even run the first scheduler (part of
    the effect control linearization) concurrently. This temporarily
    disables most of the write barrier elimination, but we will get back to
    that later.

    Drive-by-fix: Remove the dead code from ChangeLowering, and stack
    allocate the Typer in the pipeline. Also migrate the AllocateStub to a
    native code builtin, so that we have the code object + a handle to it
    available all the time.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=v8:4969
LOG=N

Review-Url: https://codereview.chromium.org/1941613002
Cr-Commit-Position: refs/heads/master@{#35938}