Tests progressive rendering. On user agents which support progressive rendering,
the content should be rendered all at once due to forward use of externalResourcesRequired on top-level SVG.
The update frequency is implementation dependant.
$RCSfile: struct-progressive-204-t.svg,v $Testing progressive rendering with external references, if supported.Rendered all at once because of forward use with externalResourcesRequired on top-level SVG$Revision: 1.5 $