If mus detects a client is janky the window-manger is informed. The code in WindowTreeClient that is called in this case can only deal with clients embedded in top-level windows (for example, ash embeds chrome and chrome is janky). The same thing happens if the creator of a top-level window embeds another client (say an OOPIF child frame). Problem is, when this happens WindowTreeClient can't determine the windows because it's supplied a client id it knows nothing about (the window manager only knows the client ids of clients it created to level windows for).

Probably the right thing to do in this case is to change the delegate notification to give the client id of the janky client *and* the client id associated with the top-level and let the WindowManager decide what to do.