WidgetObserverTest.ActivationChange fails flakily in views_mus_unittests with WS2

See work to use test_ws / ws2 in views_mus_unittests here:
  https://chromium-review.googlesource.com/c/chromium/src/+/1138749

[ RUN      ] WidgetObserverTest.ActivationChange
[127158:127162:0717/163218.101865:3992637163761:INFO:service_process_launcher.cc(200)] Launched child process pid=127172, instance=, name=test_ws, user_id=505C0EE9-3013-43C0-82B0-A84F50CF8D84
[127172:127172:0717/163218.277564:3992637339323:ERROR:window_service.cc(28)] Not implemented reached in void ui::ws2::(anonymous namespace)::BindEventInjectorRequest(ui::mojom::EventInjectorRequest)
[127172:127172:0717/163218.277805:3992637339457:ERROR:test_gpu_interface_provider.cc(16)] Not implemented reached in void (anonymous namespace)::BindGpuRequest(ui::mojom::GpuRequest)
[127172:127172:0717/163218.277977:3992637339628:ERROR:test_gpu_interface_provider.cc(22)] Not implemented reached in void (anonymous namespace)::BindDiscardableSharedMemoryManagerRequest(discardable_memory::mojom::DiscardableSharedMemoryManagerRequest)
[127172:127172:0717/163218.281741:3992637343394:ERROR:window_tree.cc(1316)] Not implemented reached in virtual void ui::ws2::WindowTree::SetHitTestMask(ui::Id, const base::Optional<gfx::Rect> &)
../../ui/views/widget/widget_unittest.cc:756: Failure
Expected equality of these values:
  toplevel1.get()
    Which is: 0x1bc67d541640
  widget_activated()
    Which is: NULL
Stack trace:
#0 0x0000006e147c testing::internal::UnitTestImpl::CurrentOsStackTraceExceptTop()
#1 0x0000006e0e59 testing::internal::AssertHelper::operator=()
#2 0x00000068f1e8 views::test::WidgetObserverTest_ActivationChange_Test::TestBody()

[1/1] WidgetObserverTest.ActivationChange (CRASHED)