DocumentExtensions
Useful methods for document objects.
Adopts the given node for the provided document context.
Creates an element of the given type or throws an exception, if
there is no such type.
Gets all downloads associated with resources of the document.
Checks if the document is waiting for a script to finish preparing.
Checks if the document has any active stylesheets that block the
scripts. A style sheet is blocking scripts if the responsible
element was created by that Document's parser, and the element is
either a style element or a link element that was an external
resource link that contributes to the styling processing model when
the element was created by the parser, and the element's style
sheet was enabled when the element was created by the parser, and
the element's style sheet ready flag is not yet set.
http://www.w3.org/html/wg/drafts/html/master/document-metadata.html#has-no-style-sheet-that-is-blocking-scripts
Spins the event loop until all stylesheets are downloaded (if
required) and all scripts are ready to be parser executed.
http://www.w3.org/html/wg/drafts/html/master/syntax.html#the-end
(bullet 3)