gfx: Implement `Debug` for `FontTemplate` instances.

components/gfx/font_template.rs

@@ -6,6 +6,7 @@ use font::FontHandleMethods;
 use platform::font::FontHandle;
 use platform::font_context::FontContextHandle;
 use platform::font_template::FontTemplateData;
+use std::fmt::{Debug, Error, Formatter};
 use std::sync::{Arc, Weak};
 use std::u32;
 use string_cache::Atom;
@@ -66,6 +67,12 @@ pub struct FontTemplate {
     is_valid: bool,
 }
 
+impl Debug for FontTemplate {
+    fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
+        self.identifier.fmt(f)
+    }
+}
+
 /// Holds all of the template information for a font that
 /// is common, regardless of the number of instances of
 /// this font handle per thread.