Fix obsolete format traits.

They are to be removed from the language in the next rust upgrade.

components/layout/inline.rs

@@ -1237,7 +1237,7 @@ impl Flow for InlineFlow {
     fn build_display_list(&mut self, layout_context: &LayoutContext) {
         // TODO(#228): Once we form lines and have their cached bounds, we can be smarter and
         // not recurse on a line if nothing in it can intersect the dirty region.
-        debug!("Flow: building display list for {:u} inline fragments", self.fragments.len());
+        debug!("Flow: building display list for {} inline fragments", self.fragments.len());
 
         let mut display_list = box DisplayList::new();
         for fragment in self.fragments.fragments.iter_mut() {

components/layout/layout_task.rs

@@ -715,7 +715,7 @@ impl LayoutTask {
             mem::transmute(&mut node)
         };
 
-        debug!("layout: received layout request for: {:s}", data.url.serialize());
+        debug!("layout: received layout request for: {}", data.url.serialize());
         debug!("layout: parsed Node tree");
         if log_enabled!(log::DEBUG) {
             node.dump();

components/layout/text.rs

@@ -41,7 +41,7 @@ impl TextRunScanner {
 
     pub fn scan_for_runs(&mut self, font_context: &mut FontContext, mut fragments: DList<Fragment>)
                          -> InlineFragments {
-        debug!("TextRunScanner: scanning {:u} fragments for text runs...", fragments.len());
+        debug!("TextRunScanner: scanning {} fragments for text runs...", fragments.len());
 
         // FIXME(pcwalton): We want to be sure not to allocate multiple times, since this is a
         // performance-critical spot, but this may overestimate and allocate too much memory.

components/layout/wrapper.rs

@@ -219,7 +219,7 @@ impl<'ln> LayoutNode<'ln> {
         }
 
         s.push_str(self.debug_str().as_slice());
-        println!("{:s}", s);
+        println!("{}", s);
 
         for kid in self.children() {
             kid.dump_indent(indent + 1);