Add two flags to customize JIT zygote.

1) -Xuseprofiledjit to do compilation of system server (and potentially
apps) at startup with a profile
2) -Xjitzygotepthreadpriority to set the zygote JIT thread priority.

Bug: 119800099
Test: m
Change-Id: I131c5a8bae0f4b15c33c3e24e07465b7858f7fe2
4 files changed