BUG ID: 5095997 (13218) Reproducible crash after call to window.close()

STEPS TO TEST:
1. Click the Open button below. A pop up window will open.
2. In the pop up window, click the Close button, being careful not to move the mouse during and shortly after clicking.

TEST PASS: The black square will be replaced by the word “SUCCESS” and Safari will not crash.

TEST FAIL: Safari will crash (the word “SUCCESS” may appear before the crash).