I'm fine removing aura_bench at this point. Not sure about aura_demo.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/de5c26563c6707dba2ef5abb97104aebd9bd3d51

commit de5c26563c6707dba2ef5abb97104aebd9bd3d51
Author: enne <enne@chromium.org>
Date: Fri Mar 25 18:03:51 2016

Remove aura_bench

This isn't used anymore.

R=piman@chromium.org
BUG=597021

Review URL: https://codereview.chromium.org/1827603002

Cr-Commit-Position: refs/heads/master@{#383302}

[modify] https://crrev.com/de5c26563c6707dba2ef5abb97104aebd9bd3d51/BUILD.gn
[modify] https://crrev.com/de5c26563c6707dba2ef5abb97104aebd9bd3d51/build/gn_migration.gypi
[modify] https://crrev.com/de5c26563c6707dba2ef5abb97104aebd9bd3d51/ui/aura/BUILD.gn
[modify] https://crrev.com/de5c26563c6707dba2ef5abb97104aebd9bd3d51/ui/aura/aura.gyp
[delete] https://crrev.com/28472efddd70ac4affc0ba9a46a56697937840a3/ui/aura/bench/DEPS
[delete] https://crrev.com/28472efddd70ac4affc0ba9a46a56697937840a3/ui/aura/bench/bench_main.cc