Root svg transform inconsistent with Chromium/Firefox/Inkscape

I have found that resvg renders this SVG inconsistently with Chromium/Firefox/Inkscape:

<svg xmlns="http://www.w3.org/2000/svg" height="1000" transform="scale(.5)" viewBox="5 5 100 100" width="1000">
  <g>
    <circle cx="10" cy="10" r="3" stroke="black" stroke-width=".1"/>
    <circle cx="20" cy="10" r="3" stroke="black" stroke-width=".1"/>
    <line stroke="black" stroke-width=".1" x1="10" x2="20" y1="10" y2="10"/>
  </g>
</svg>

Here's a comparison of the output of Firefox/Chromium/Inkscape (left) and resvg (right):

I suspect the culprit here is probably the transform on the root SVG coupled with viewBox. I believe the support for transform on the svg element was added in SVG 2 and there have been inconsistencies among implementations in the past (see f.e. https://lists.w3.org/Archives/Public/www-svg/2015May/0024.html).

The output of resvg seems to be equivalent to rendering the following SVG with f.e. Firefox:

<svg xmlns="http://www.w3.org/2000/svg" height="1000" viewBox="5 5 100 100" width="1000">
  <g transform="scale(.5)">
    <circle cx="10" cy="10" r="3" stroke="black" stroke-width=".1"/>
    <circle cx="20" cy="10" r="3" stroke="black" stroke-width=".1"/>
    <line stroke="black" stroke-width=".1" x1="10" x2="20" y1="10" y2="10"/>
  </g>
</svg>

Might be related to #874.

Start with the minimal SVG reproduction in the issue and compare resvg with Chromium, Firefox, and Inkscape. Inspect how root SVG transforms interact with the viewBox, using issue #874 as related context. Done means resvg renders the root transform consistently with the other implementations.