Recently we changed feedback vector allocation to be based on the
bytecode size of the function. The threshold at which the feedback
vectors are allocated was set to 12 * bytecode size of the function.
This caused a couple of regressions on IC:duration and some regressions
on other benchmarks. To avoid these regressions this cl reduces the
scale factor to 8 instead of 12.

Bug: chromium:1187733
Change-Id: I0553d368434499cc52a6e786b5de6d6b954e6546
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2778295
Commit-Queue: Mythri Alle <mythria@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73624}