I'm about to file a CL for intrinsic size calculation, which will deal more correctly with floats. However, this is going to make us "better" at it than the others (Edge, Firefox, Blink legacy).

<div id="stf" style="position:absolute;">
  <div id="f1" style="float:left; width:10px; height:10px;"></div>
  <div id="wrapper">
    <div id="f2" style="float:left; width:10px; height:10px;"></div>
  </div>
</div>

#f1 and #f2 get stacked vertically in Edge, Firefox and Blink legacy.
Without #wrapper, they are all able to place #f1 and #f2 beside each other, though.

I'm pretty sure slightly older versions of Internet Explorer (like IE10) were able to pass such a test, but I suspect that they had to  "dumb down" the intrinsic width calculation machinery to match the others.
 

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