The GrabWindowSnapshotTest fails on MacOS 10.11 and above. See error log below. I could reproduce this on a 10.12 macbook and traced this down to CGWindowListCreateImage in snapshot_mac.cc, which returns a 1x1 pixel image.

But I don't know what is causing this. Maybe the window is set up wrongly in the test?

The test is disabled on the Mac10.11 builder at the moment. It was not run on the bots for a long time, so there's likely no culprit CL. Thus, I'm assuming that this problem was introduced with MacOS 10.11. See also https://codereview.chromium.org/2592983002/, where the tests were enabled on the bots.

Failure log:
https://uberchromegw.corp.google.com/i/chromium.mac/builders/Mac10.11%20Tests/builds/6881

[ RUN      ] GrabWindowSnapshotTest.TestGrabWindowSnapshot
../../ui/snapshot/snapshot_mac_unittest.mm:45: Failure
Value of: CGImageGetWidth([rep CGImage])
  Actual: 1
Expected: 400 * scaleFactor
Which is: 400
../../ui/snapshot/snapshot_mac_unittest.mm:49: Failure
Expected: (red + green + blue) >= (3.0), actual: 0 vs 3
[  FAILED  ] GrabWindowSnapshotTest.TestGrabWindowSnapshot (31 ms)