Now that Asm.js code is also context independent, move code to ensure context independence
from BytecodeGenerator to FinalizeUnoptimizedCode.

Change-Id: I7738eb3b347ea82764ecd3b5548dc82cb06d2f4e
Reviewed-on: https://chromium-review.googlesource.com/c/1347483Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57730}