These are no longer necessary since we only have one optimizing compiler.
Also avoid changing --turbo-filter when --no-opt is set, and instead
explicitly check both the FLAG_opt and FLAG_turbo_filter in 
GetOptimizedCode to check whether optimization is disabled.

BUG=v8:6408

Change-Id: I0948f788e8ff111c08022270d86c22f848da300a
Reviewed-on: https://chromium-review.googlesource.com/568484
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46648}