Revert^2 "Refactor code around JIT creation."

This reverts commit 763cd98161424cf19af2f113a6802f04860dcd6e.

Bug: 119800099

Reason for revert: Updated the DCHECKo take into account current state
of zygote not having a thread pool.

Change-Id: I1181ff85e7aebd062ee892548b80ab3de06a5ac7
10 files changed