Parse formal parameters.

dart/frog/leg/scanner/listener.dart

Index: dart/frog/leg/scanner/listener.dart
diff --git a/dart/frog/leg/scanner/listener.dart b/dart/frog/leg/scanner/listener.dart
index 5b809605ec70b0aa8415ff2902d0b3507dfc48b4..8701a9eb7aca73935caae88cc9c07b26198bd96e 100644
--- a/dart/frog/leg/scanner/listener.dart
+++ b/dart/frog/leg/scanner/listener.dart
@@ -27,6 +27,12 @@ class Listener {
   void endExpressionStatement(Token token) {
   }
 
+  void beginFormalParameter(Token token) {
+  }
+
+  void endFormalParameter(Token token) {
+  }
+
   void beginFormalParameters(Token token) {
   }
 
@@ -154,6 +160,9 @@ class Listener {
   void handleNoArguments(Token token) {
   }
 
+  void handleNoType(Token token) {
+  }
+
   void handleNoTypeVariables(Token token) {
   }
 
@@ -372,6 +381,12 @@ class BodyListener extends ElementListener {
     onError = handleOnError; // Cuts parser time in half or more.
   }
 
+  void endFormalParameter(Token token) {
+    NodeList name = new NodeList.singleton(popNode());
+    TypeAnnotation type = popNode();
+    pushNode(new VariableDefinitions(type, null, name, token));
+  }
+
   void endFormalParameters(int count, Token beginToken, Token endToken) {
     pushNode(makeNodeList(count, beginToken, endToken, ","));
   }