Local refactoring to replace if cascade by switch. For readability and
performance.

R=ahaas@chromium.org

Change-Id: I064d51c7c8232fefcde223b086eb7b9caf44f94c
Reviewed-on: https://chromium-review.googlesource.com/485480
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44798}