Chrome Version: (copy from chrome://version)
OS: (e.g. Win7, OSX 10.9.5, etc...)

What steps will reproduce the problem?
(1) I accidentally landed a CL adding some OWNERS and some comments, but it turns out that same-line #comments are invalid in OWNERS files.
 (https://codereview.chromium.org/2921663004/)

What is the expected result?
Presubmit failure

What happens instead?
The patch was able to be landed, which broke presubmit for people working in WebKit/Source/core/css and WebKit/Source/core/style for a short time (until https://codereview.chromium.org/2970643002/ landed)



I started an attempt at writing a PanProject presubmit in https://chromium-review.googlesource.com/c/559024/ (note: this CL is still a bit of a mess and doesn't actually work yet), but I got a bit stuck...