Created attachment 375493 [details]
Open the attached test case.
Expected: No alert messages and child <rect> element fills the whole SVG client rect.
Result: An alert message is invoked and the intrinsic with of the SVG is wrong.
Related WPT test is: https://wpt.fyi/results/svg/coordinate-systems/outer-svg-intrinsic-size-001.html?label=master&label=experimental
Similarly, the SVG intrinsic height is not calculated correctly if the width attribute is removed and the viewBox attribute is set.
Related WPT test is: https://wpt.fyi/results/svg/coordinate-systems/outer-svg-intrinsic-size-002.html?label=master&label=experimental