Auto merge of #9603 - Ms2ger:document-bc, r=jdm

Store a pointer to the browsing context in the Document.

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components/script/dom/xmlhttprequest.rs

@@ -1230,6 +1230,7 @@ impl XMLHttpRequest {
             DOMString::from(format!("{}", mime))
         });
         Document::new(win,
+                      None,
                       parsed_url,
                       is_html_document,
                       content_type,