Super-w resizes maximized windows, lowering performance during animation

[Benjamin Xiao]

Super-w resizes maximized windows and lowers the performance of the Window Picker zoom animation.

Current behavior:
Super-w causes maximized windows to be resized in Window Picker mode. This causes unnecessary repainting of windows when switching apps using Window Picker, which lowers the performance of the zoom animation and gives the desktop a feeling of sluggishness. Because the maximized windows are getting resize events, this also causes some unwanted behavior in certain applications. For example, triggering Super-w with a maximized Virtualbox window will cause the guest VM to resize its desktop, which is a very lengthy and slow operation.

Expected behavior:
Maximized windows should NOT be resized.

Steps to reproduce:
1.) Open two maximized browser windows with a webpage that stretches all the way to the bottom of the windows. Note where the webpage gets cut off by the boundaries of the windows.
2.) Press Super-w to toggle Window Picker. Note that the webpages in the Window Picker previews are now cut off even more on the bottom. This is because the window has been resized and the bottom of the window is now higher up. Also note the choppy performance of the animation for the maximized windows as compared to non-maximized windows.
3.) Press Super-w again. This will trigger another resize event, restoring the windows to their maximized states.

Extra Information:
1.) The amount of space that is being resized seems to be the same size as the global menu, which leads me to believe that it is related. After all, maximized windows have their titlebars merged with the global menu. Perhaps Unity is miscalculating the size of the windows because of this.