Implement dynamic measuring

[hartman]

Currently we depend on preconceptions of the layout of the control bar to determine which layout is chosen. Ideally, we do a dynamic measure step, whereby due to applying a class, measuring to see if it fits, and alternatively switching back, or even to a next class, we determine if the class fits or not.

The complexity here is that we need to prevent flipping back and forth between two states. We need to 'measure' and then 'settle'.

[hartman]

Idea:

We could just have defined widths, for each 4 layouts. The reason I have so far not done so, is because of the optional presence of so many of the controls... That means that in one configuration, you can have 5 controls on the side for one video, and just 2 for another... that is a huge difference in width, making it rather difficult to be consistent.

The new idea however, is that you would have an 'overflow' bar that could reveal the rest of the controls in a sort of 'hover' overlay..