I do scan the equivalent mac-reviews@ list regularly, so I guess this could be useful, but I don't see a pressing need for it. It's harmless to add though.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/tools/depot_tools/+/7227d2175a9efdf5c1b9482e6fae0e5e5b00b3de

commit 7227d2175a9efdf5c1b9482e6fae0e5e5b00b3de
Author: Daniel Cheng <dcheng@chromium.org>
Date: Mon Nov 20 21:57:42 2017

Add OutputApi.AppendCC to allow presubmit checks to add CCs

Bug:  786386 
Change-Id: If29acf287355d150e0f89f45b2f7aa87a08dcc57
Reviewed-on: https://chromium-review.googlesource.com/776645
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>

[modify] https://crrev.com/7227d2175a9efdf5c1b9482e6fae0e5e5b00b3de/tests/presubmit_unittest.py
[modify] https://crrev.com/7227d2175a9efdf5c1b9482e6fae0e5e5b00b3de/presubmit_support.py
[modify] https://crrev.com/7227d2175a9efdf5c1b9482e6fae0e5e5b00b3de/git_cl.py
[modify] https://crrev.com/7227d2175a9efdf5c1b9482e6fae0e5e5b00b3de/tests/git_cl_test.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7052cdff011ef8388da98514bf9c95a18ca02338

commit 7052cdff011ef8388da98514bf9c95a18ca02338
Author: Daniel Cheng <dcheng@chromium.org>
Date: Tue Nov 21 19:23:29 2017

Auto-CC ipc-security-reviews@ when changing IPC-related files.

Bug:  786386 
Change-Id: I28d5809389aa86ee274b17725ca5312d4b8bb3ae
Reviewed-on: https://chromium-review.googlesource.com/776411
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#518329}
[modify] https://crrev.com/7052cdff011ef8388da98514bf9c95a18ca02338/PRESUBMIT.py
[modify] https://crrev.com/7052cdff011ef8388da98514bf9c95a18ca02338/PRESUBMIT_test_mocks.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/tools/depot_tools/+/d36fce44086cd531a01ee91114ff2955c502a603

commit d36fce44086cd531a01ee91114ff2955c502a603
Author: Daniel Cheng <dcheng@chromium.org>
Date: Thu Nov 23 02:50:12 2017

Fix silly bug in presubmit_support implementation of AppendCC.

The executor needs to accumnulate more_cc, not overwrite them.

Bug:  786386 
Change-Id: Iadfe836ae9623f1b66d2db8209d347b5e61ccae8
Reviewed-on: https://chromium-review.googlesource.com/784553
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>

[modify] https://crrev.com/d36fce44086cd531a01ee91114ff2955c502a603/presubmit_support.py

Firehose successfully established: https://groups.google.com/a/chromium.org/forum/#!forum/ipc-security-reviews