Some bailout reasons are never referenced. Removing these allows us to
decrease the size of bailout reason bit-fields to 7 bits.

Change-Id: Ib5e884d224c12313e06493ed05a18a22b3951665
Reviewed-on: https://chromium-review.googlesource.com/596128
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47077}