Other fuzzers already have this ability. This CL adds it to the fuzzer.
The input has to be valid bytes, otherwise we cannot generate the text
representation.

R=titzer@chromium.org
CC=gdeepti@chromium.org

Change-Id: If1ba8accc707bee3b042e93f4201949f0233c90e
Reviewed-on: https://chromium-review.googlesource.com/1109794
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53926}