Revert of [turbofan] Add initial support for global specialization. (patchset #4 id:60001 of https://codereview.chromium.org/1387393002/ )

Reason for revert:
Breaks GC stress: http://build.chromium.org/p/client.v8/builders/V8%20Linux64%20GC%20Stress%20-%20custom%20snapshot/builds/1984/steps/Bisect%20c5528ac1.Retry/logs/regress-crbug-450960

Original issue's description:
> [turbofan] Add initial support for global specialization.
>
> Introduce a new JSGlobalSpecialization advanced reducer that runs
> during the initial inlining and context specialization, and specializes
> the graph to the globals of the native context.  Currently we assume
> that we do not inline cross native context, but long-term we will grab
> the global object from the JSLoadGlobal/JSStoreGlobal feedback (with the
> new global load/store ICs that are currently in the workings), and then
> this whole specialization will be fully compositional even across
> cross-context inlining.
>
> Note that we cannot really handle most of the stores to global object
> property cells because TurboFan doesn't have a mechanism to enforce
> certain representations.  Also note that we cannot yet fully benefit
> from the type feedback collected on the global object property cells,
> because the type system cannot deal with maps in a reasonable way.
>
> CQ_INCLUDE_TRYBOTS=tryserver.v8:v8_linux_nosnap_rel
> R=jarin@chromium.org
> BUG=v8:4470
> LOG=n
>
> Committed: https://crrev.com/6fbf7903f94924ea066af481719898bd9667b6eb
> Cr-Commit-Position: refs/heads/master@{#31139}

TBR=jarin@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4470

Review URL: https://codereview.chromium.org/1390073004

Cr-Commit-Position: refs/heads/master@{#31144}