By representing "optimization disabled" with a kNoReason bailout reason,
we have enough spare bits to merge the bailout reason field into
compiler hints. This decreases SFI size by one word.

Change-Id: I0169c91dfbfa443128b060a83e483717ed31a166
Reviewed-on: https://chromium-review.googlesource.com/595980
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47080}