... when above a certain minimum threshold. This is to guard against
memory running away in scenarios where the JS heap is empty and
there's only high throughput C++ allocations that don't allow for a
memory reducer GC to kick in.

This logic should be revisited after Oilpan's young generation
collector is implemented which may allow switching to a more efficient
shrinking strategy for initial heap setup.

Bug: chromium:1029379, chromium:1300028, chromium:1300492
Change-Id: I93924fc2fe77d6226c29358d3afb1cc9d6fbf3b1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3484319Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79255}