cloneNode(true) round-tripped through a throwaway <div>'s innerHTML, so the
HTML fragment parser discarded elements that are not valid children of <div>
(<tr>, <td>, <option>, <tbody>, …) — createElement('tr').cloneNode(true)
returned null — and JS-set inline styles were lost. The shallow path also
re-derived attributes by regex-scraping serialized HTML.
Clone structurally with real DOM APIs: shallow-clone each node via
createElement/createElementNS plus a getAttributeNames() attribute copy (no
parsing context, every attribute preserved), then descend into children with an
explicit stack so a deep subtree cannot overflow the JS stack. Text, Comment,
DocumentFragment and <template> contents are handled.
Fixes#490
Andrey Mnatsakanov
491ecfb0f1