This lead to link errors in an unrelated CL. The function was declared
with "const PrintableInstructionBlock&", but defined with
"PrintableInstructionBlock&".

R=mstarzinger@chromium.org

Change-Id: I08a9837dc44dc9d8f508c914da92549179a6790e
Reviewed-on: https://chromium-review.googlesource.com/1088910Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53560}