Comment 3 for bug 1059244

This bug isn't a duplicate of 419266, instead this bug is because of the way plain svg is generated in extension/internal/svg.cpp, the duplication of the document's root removes all comments and PI nodes that came before the root.

To fix this, a duplicate document function must be added to our xml library. this must duplicate the document node itself (not the root node) and must return a document node (the current duplicate returns an normal node only)