Comment 7 for bug 1690952

The size of the rectangle is irrelevant. It does not establish a viewport size. The marker is being rendered by all browsers and Inkscape without scaling due to a view port. The inconsistency is that Inkscape is not properly clipping the marker. The browsers (Opera/Chrome/Firefox) clip the marker to a 3x3 square (or 300x300 square after the <svg> viewBox and 10px stroke width is accounted for). This can be seen by adding a stroke to the rectangle in the marker. All browsers and Inskcape give the same rendering when 'overflow' is set to 'visible' on the <marker> element.