Second round of cleanups for new optional parameter semantics.

lib/compiler/implementation/scanner/listener.dart

Index: lib/compiler/implementation/scanner/listener.dart
===================================================================
--- lib/compiler/implementation/scanner/listener.dart	(revision 13754)
+++ lib/compiler/implementation/scanner/listener.dart	(working copy)
@@ -585,7 +585,7 @@
     return token;
   }
 
-  void recoverableError(String message, [Token token, Node node]) {
+  void recoverableError(String message, {Token token, Node node}) {
     if (token == null && node != null) {
       token = node.getBeginToken();
     }
@@ -984,7 +984,7 @@
     return skipToEof(token);
   }
 
-  void recoverableError(String message, [Token token, Node node]) {
+  void recoverableError(String message, {Token token, Node node}) {
     listener.cancel(message, token: token, node: node);
   }
 
@@ -1748,7 +1748,7 @@
     listener.log(message);
   }
 
-  void internalError([Token token, Node node]) {
+  void internalError({Token token, Node node}) {
     listener.cancel('internal error', token: token, node: node);
     throw 'internal error';
   }