Add missing scanner.expectDone() calls.

lib/src/parse/at_root_query.dart

@@ -26,6 +26,7 @@ class AtRootQueryParser extends Parser {
         atRules.add(identifier().toLowerCase());
         whitespace();
       } while (lookingAtIdentifier());
+      scanner.expectDone();
 
       return new AtRootQuery(include, atRules);
     });

lib/src/parse/keyframe_selector.dart

@@ -28,6 +28,7 @@ class KeyframeSelectorParser extends Parser {
         }
         whitespace();
       } while (scanner.scanChar($comma));
+      scanner.expectDone();
 
       return selectors;
     });

lib/src/parse/media_query.dart

@@ -19,6 +19,7 @@ class MediaQueryParser extends Parser {
         whitespace();
         queries.add(_mediaQuery());
       } while (scanner.scanChar($comma));
+      scanner.expectDone();
       return queries;
     });
   }