<b>Version: <Kenneth, what is the frequency?></b>
<b>OS: <please tell me it's not XP></b>

What steps will reproduce the problem?
(1) https://mounirlamouri.github.io/sandbox/media/dynamic-controls.html
(2) set width to 140
(3) observe that the full screen button is not entirely visible

i've seen this issue before and forgot to write it up.  in MediaControls::computeWhichControlsFit, it ignores the 18px margin that the sliders have.

it should really pay attention to margin of all the controls.  it's probably also a good idea to make the algorithm stop adding lower priority controls once a higher-priority one is dropped.  otherwise, it looks weird as controls appear then disappear as the bar gets wider.  right now, the controls are all the same width so this never happens.