Also revert "[heap] Force inlining of AllocatedSinceLastGC"

This is a speculative revert to see if it actually impacts the benchmarks in
question.

This reverts commit 723e120b.
This reverts commit 08dbdd40.

BUG=chromium:605524
LOG=N
TBR=ulan@chromium.org

Review-Url: https://codereview.chromium.org/1932883002
Cr-Commit-Position: refs/heads/master@{#35881}