Build: https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Mac10.12%20Tests/16328


Relevant part from stack trace:
../../chrome/browser/ui/cocoa/apps/native_app_window_cocoa_browsertest.mm:198: ERROR: this mock object (used in test NativeAppWindowCocoaBrowserTest.HideShowWithAppWithShim) should be deleted but never is. Its address is @0x7fb48bde0810.
ERROR: 1 leaked mock object found at program exit. Expectations on a mock object is verified when the object is destructed. Leaking a mock means that its expectations aren't verified, which is usually a test bug. If you really intend to leak a mock, you can suppress this error using testing::Mock::AllowLeak(mock_object), or you may use a fake or stub instead of a mock.


https://chromium-review.googlesource.com/c/chromium/src/+/1305889 seems suspicious. So, assigning to ccameron@ for further triage.