This makes the code dealing with type feedback more concise and uniform
(at the cost of a few redundant comparisons).

Bug: 
Change-Id: If6b98bd1f0dddd392d7b00d65b600127bd30ff7e
Reviewed-on: https://chromium-review.googlesource.com/818984
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50035}