Factory::NewUninitializedFixedArray is unsafe for GC. If performance
allows, we should remove the function.

Change-Id: I3f80352797e9768b788c2996c3f29e823c067f74
Reviewed-on: https://chromium-review.googlesource.com/517794Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46166}