Not sure what I did. And I'm not sure what it is called. I have a dual monitor setup with 15.04. I used to be able to grab a window, move it to the other monitor, and kind of "throw" it to the top and it would maximize itself to the monitor. I did something, and it no longer does this. I have to double-click the title bar now to get it to maximize.

How would I fix such behavior?