Store the Page's final URL before parsing

We were parsing URLs like

    //bits.wikimedia.org/static-1.22wmf22/skins/vector/images/search-ltr.png?303-4

as local filenames because HTMLImageElement::update_image didn't have a
current_url to pass to make_url().

src/components/script/html/hubbub_html_parser.rs

@@ -129,7 +129,6 @@ pub enum HtmlDiscoveryMessage {
 pub struct HtmlParserResult {
     root: AbstractNode<ScriptView>,
     discovery_port: Port<HtmlDiscoveryMessage>,
-    url: Url,
 }
 
 trait NodeWrapping {
@@ -350,6 +349,17 @@ pub fn parse_html(cx: *JSContext,
     let url2 = load_response.metadata.final_url.clone();
     let url3 = url2.clone();
 
+    // Store the final URL before we start parsing, so that DOM routines
+    // (e.g. HTMLImageElement::update_image) can resolve relative URLs
+    // correctly.
+    //
+    // FIXME: is this safe? When we instead pass an &mut Page to parse_html,
+    // we crash with a dynamic borrow failure.
+    let page = page_from_context(cx);
+    unsafe {
+        (*page).url = Some((url2.clone(), true));
+    }
+
     // Build the root node.
     let root = @HTMLHtmlElement { htmlelement: HTMLElement::new(HTMLHtmlElementTypeId, ~"html", document) };
     let root = unsafe { Node::as_abstract_node(cx, root) };
@@ -595,7 +605,6 @@ pub fn parse_html(cx: *JSContext,
     HtmlParserResult {
         root: root,
         discovery_port: discovery_port,
-        url: load_response.metadata.final_url,
     }
 }
 

src/components/script/script_task.rs

@@ -699,14 +699,13 @@ impl ScriptTask {
                                                                  self.constellation_chan.clone());
 
 
-        let HtmlParserResult {root, discovery_port, url: final_url} = html_parsing_result;
+        let HtmlParserResult {root, discovery_port} = html_parsing_result;
 
         // Create the root frame.
         page.frame = Some(Frame {
             document: document,
             window: window,
         });
-        page.url = Some((final_url, true));
 
         // Send style sheets over to layout.
         //