This text should not be autosized (its computed font size should remain 16px), since the position:fixed causes it to be considered to have constrained height.
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

This text should be autosized to 40px computed font size, since it is within a float:left, so constrained height is no longer a concern.
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor.

This text should not be autosized (its computed font size should remain 16px), since the position:absolute causes it to be considered to have constrained height.
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

This text should be autosized to 40px computed font size, since it is within an overflow:auto, so constrained height is no longer a concern.
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor.