Don't load all font faces sources

We stop at the first one we manage to load.

components/style/font_face.rs

@@ -7,7 +7,6 @@ use cssparser::{AtRuleParser, DeclarationListParser, DeclarationParser, Parser};
 use parser::{ParserContext, log_css_error};
 use properties::longhands::font_family::parse_one_family;
 use std::iter;
-use std::slice;
 use url::Url;
 
 #[derive(Clone, Debug, HeapSizeOf, PartialEq, Eq, Deserialize, Serialize)]
@@ -60,21 +59,15 @@ pub fn parse_font_face_block(context: &ParserContext, input: &mut Parser)
     }
 }
 
-pub struct EffectiveSourcesIter<'a>(slice::Iter<'a, Source>);
+#[derive(Clone, Debug, Deserialize, Serialize)]
+pub struct EffectiveSources(Vec<Source>);
 
 impl FontFaceRule {
     /// Returns the list of effective sources for that font-face, that is the
     /// sources which don't list any format hint, or the ones which list at
     /// least "truetype" or "opentype".
-    pub fn effective_sources(&self) -> EffectiveSourcesIter {
-        EffectiveSourcesIter(self.sources.iter())
-    }
-}
-
-impl<'a> iter::Iterator for EffectiveSourcesIter<'a> {
-    type Item = &'a Source;
-    fn next(&mut self) -> Option<&'a Source> {
-        self.0.find(|source| {
+    pub fn effective_sources(&self) -> EffectiveSources {
+        EffectiveSources(self.sources.iter().rev().filter(|source| {
             if let Source::Url(ref url_source) = **source {
                 let hints = &url_source.format_hints;
                 // We support only opentype fonts and truetype is an alias for
@@ -86,7 +79,14 @@ impl<'a> iter::Iterator for EffectiveSourcesIter<'a> {
             } else {
                 true
             }
-        })
+        }).cloned().collect())
+    }
+}
+
+impl iter::Iterator for EffectiveSources {
+    type Item = Source;
+    fn next(&mut self) -> Option<Source> {
+        self.0.pop()
     }
 }