Factory::NewRawOneByteString initializes the string length without
atomic accessor. This leads to data race if the string is pretenured
and black allocated because the concurrent marker loads the string
length before checking the string markbits.

This patch changes the order to check the markbits first.

Bug: v8:8579
Change-Id: Ic434f7dde9baa6264fe133499d2394c0d4cc5394
Reviewed-on: https://chromium-review.googlesource.com/c/1388542
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58465}