Prototype exo/wayland fuzzer

As part of go/exonerate, we are aiming to implement a fuzzer with >80%
coverage by July. This CL contains the prototype of that fuzzer.

We also create and ship a unit-test which performs an example iteration
of the fuzzer. The purpose of this test is to prevent the fuzzer code
from stagnating over time.

Bug: 961564
Change-Id: I131290b38fae8227225563abb3fa0a8dd8c83e57
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1640526
Reviewed-by: Oliver Chang <ochang@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Nic Hollingum <hollingum@google.com>
Cr-Commit-Position: refs/heads/master@{#667822}
12 files changed