It seems like gOverridingLogicalWidthLengthMap/gOverridingLogicalHeightLengthMap are not getting cleared properly at the end of layout. This is indicated when running fast/transferred-sizes-respect-definite-sizes.html. If you go directly to the test by putting the URL in the search bar, two layouts will be performed. On the second layout, the flex item div will get its width computed through the shouldComputeLogicalWidthFromAspectRatio branch because it has entries inside of gOverridingLogicalHeightLengthMap. However, this should not be happening since the map should be cleared at the end of the first layout.