Some tests in test/window_test.dart are skipped in Safari.

In Safari the test passes in isolation. However, when running all tests at once, the whole batch fails. It's hard to tell why. There seems to be some cross-tests state pollution going on. Perhaps the issue is that tests run in an <iframe> and location history is modifying some global state.

Sample failure: https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8804297826222711985/+/u/test:_Run_tests_on_macOS_Safari/stdout

Edit by @yjbanov: refined this bug report with more details.