SVG files with comments aren't correctly scaled in QML

SVG files beginning with a comment (before the <svg> tag) are always rendered at the intrinsic size - as if Image.sourceSize wasn't specified. An identical file without the comment will be rendered at the correct scale.

Adobe Illustrator outputs SVGs like this by default.

A small testcase is attached. It will draw a raster-scaled triangle from triangle.svg and vector-scaled triangle from triangle2.svg. The files are identical, other than the comment.