Transform scale() combined with a devicePixelRatio creates roundoff errors

• Component: Accessibility
• Status: NEW ---

[Tom Dezentje]

When a browser has a devicePixelRatio with decimals there seems to be a roundoff error.
As shown in the following example: https://jsfiddle.net/xb813adh

The red bar is always 100px and scales accordingly.
The blue bar is 1px width scaled with a transform. It should always be the same width as the red bar.

When zooming in the width of the blue bar stays the same for 1, 1.10 and 1.25. 
After that it stays the same until a scale of 2.

Changing the example to scale 50px 2 times gives minor roundoff errors but is still incorrect.
Seen here: https://jsfiddle.net/y9jg10hp/

Other browsers show the correct working.

[Radar WebKit Bug Importer]

<rdar://problem/48667104>