This reverts commit d3104923.

Reason for revert: Breaks win debug, causes lots of timeouts.
https://build.chromium.org/p/client.v8/builders/V8%20Win64%20-%20debug/builds/20387

Original change's description:
> Implement and use VectorSegment to avoid repeated allocation of ZoneVector properties.
> 
> The parser holds a single vector whose backing storage is reused in calls
> to ParseJsonObject, so that once we reach the peak number of unstored
> properties no more allocations are required.
> 
> This improves performance of parsing inputs like those in Speedometer VanillaJS
> by about 2% in my local measurement, and would presumably do better on more
> pathological inputs.
> 
> This should also have the side effect of reducing peak memory usage at this time
> slightly, since we do fewer zone allocations which cannot be freed until the
> parse finishes.
> 
> Bug: chromium:771227
> Change-Id: I8aa1514b37a74f82539f95f94292c8fa1582d66a
> Reviewed-on: https://chromium-review.googlesource.com/789511
> Reviewed-by: Camillo Bruni <cbruni@chromium.org>
> Reviewed-by: Marja Hölttä <marja@chromium.org>
> Commit-Queue: Jeremy Roman <jbroman@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#49693}

TBR=jbroman@chromium.org,marja@chromium.org,cbruni@chromium.org

Change-Id: I5b198aeffed6f1543f6110709dc74b311d4ba144
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:771227
Reviewed-on: https://chromium-review.googlesource.com/796151Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49705}