ShellTest.SkipAndSubmitFrame is flaky #66056
Description
Saw this fail on the Linux Host Engine host_release build today:
[ RUN ] ShellTest.SkipAndSubmitFrame
../../flutter/shell/common/shell_unittests.cc:1039: Failure
Expected equality of these values:
1
external_view_embedder->GetSubmittedFrameCount()
Which is: 2
Build: https://ci.chromium.org/p/flutter/builders/prod/Linux%20Host%20Engine/6861
Log: https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket.appspot.com/8868899425341347024/+/steps/Host_Tests_for_host_release/0/stdout
Test binary in question: shell_unittests