Unable to find the possible suspect using Find it and CL.
Using Code Search for the file, "!activating_ in system_tray.cc" assigning to the concern owner.

Suspecting the CL --
https://chromium.googlesource.com/chromium/src/+/78cffd731645283982ec8821a054b67317ee3b8a

@estade -- Could you please look into the issue, kindly re-assign if this is not related to your change.
Thank You.

Looks like Oshima just added that check ---  bug 651242 

ClusterFuzz has detected this issue as fixed in range 440631:440646.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=6193078307389440

Fuzzer: attekett_surku_fuzzer
Job Type: linux_asan_chrome_chromeos
Platform Id: linux

Crash Type: CHECK failure
Crash Address: 
Crash State:
  !activating_ in system_tray.cc
  ash::SystemTray::ActivationObserver::OnWindowActivated
  ash::WmShellAura::OnWindowActivated
  
Sanitizer: address (ASAN)

Fixed: https://cluster-fuzz.appspot.com/revisions?job=linux_asan_chrome_chromeos&range=440631:440646

Unminimized Testcase: https://cluster-fuzz.appspot.com/download/AMIfv94IpnnDen7n9CYSPIqscp5d41poDvLZjEpokjb5XVYj1DQOeu2NFn2oufSqpOI6JG6XkJzlKwxDfZeEoD1l1CZuRebxqBTq_s3EBWjx5bbKWrsIqgAkL92D8TzCAstnz_4HUcZKHTIbGgSa49Q-AVZ91Pytxw?testcase_id=6193078307389440


Additional requirements: Requires Gestures

See https://dev.chromium.org/Home/chromium-security/bugs/reproducing-clusterfuzz-bugs for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.

ClusterFuzz testcase 6193078307389440 is verified as fixed, so closing issue.

If this is incorrect, please add ClusterFuzz-Wrong label and re-open the issue.