Mouseevent On Closeddoc

BUG ID: 4229177 REGRESSION (Denver): crash dispatching mouse events (4608)

STEPS TO TEST: Click on the link below, and move your mouse cursor over the blank page that is loaded.

TEST PASS: No crash after moving the mouse over the blank page that is loaded. Nothing happens.

TEST FAIL: Crash after moving the mouse over the blank page that opens.

Click this link