This reverts commit 1f0b0ed0.

Reason for revert: still crashing https://ci.chromium.org/ui/p/chromium/builders/try/android-marshmallow-arm64-rel/877258/test-results

Original change's description:
> Reland "heap: Fix initial GC configuration for C++-only heaps"
>
> This is a reland of 7ef67b2e
>
> Manually checked that the CL was not the culprit breaking
>   media_blink_unittests --gtest_filter=WebMediaPlayerImplTest.MemDumpReporting
>
> Original change's description:
> > heap: Fix initial GC configuration for C++-only heaps
> >
> > Heaps in V8 start with a large limit that is shrunk upon young
> > generation GCs, based on some liveness estimate. This provides best
> > throughput during startup while at the same time finding a reasonable
> > first limit.
> >
> > For C++ (embedder memory) there is no estimate which is why it was
> > piggy-backing on V8. This breaks in scenarios where no JS memory is
> > allocated.
> >
> > In this fix we start a memory reducer after embedder memory has hit
> > the activation threshold if no GC happened so far. As soon as a single
> > Scavenger has happened, we leave it up to the JS estimate to figure
> > out a limit. Memory reducing GCs will then find a regular limit based
> > on the initial live size.
> >
> > Drive-by: Give embedders the same activiation threshold of 8MB as JS.
> >
> > Bug: chromium:1217076
> > Change-Id: I8469696002ac2af8d75d6b47def062d2608387a1
> > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2944935
> > Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
> > Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#75012}
>
> Bug: chromium:1217076
> Change-Id: I482d8525379e33095834d5b41be8bb49bdd8a5d4
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2949094
> Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
> Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
> Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
> Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#75048}

Bug: chromium:1217076
Change-Id: Ia409d7a3a22127af749cff5eb5db1ff508b969e4
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2951468
Auto-Submit: Sathya Gunasekaran  <gsathya@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#75068}