AST nodes for function-typed 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 1c4559c111fc65c3fa2cea8836912ec217095871..25a46ff8ad04ad4e23af41da6649ae11a0fba96a 100644
--- a/dart/frog/leg/scanner/listener.dart
+++ b/dart/frog/leg/scanner/listener.dart
@@ -1057,9 +1057,12 @@ class NodeListener extends ElementListener {
   }
 
   void handleFunctionTypedFormalParameter(Token token) {
-    canceler.cancel('function typed formal parameters are not implemented',
-                    token: token);
-    NodeList parameters = popNode();
+    NodeList formals = popNode();
+    Identifier name = popNode();
+    TypeAnnotation returnType = popNode();
+    pushNode(null); // Signal "no type" to endFormalParameter.
+    pushNode(new FunctionExpression(name, formals, null, returnType,
+                                    null, null));
   }
 
   void handleValuedFormalParameter(Token equals, Token token) {