Parse argument definition test expressions.

dart/lib/compiler/implementation/scanner/listener.dart

Index: dart/lib/compiler/implementation/scanner/listener.dart
diff --git a/dart/lib/compiler/implementation/scanner/listener.dart b/dart/lib/compiler/implementation/scanner/listener.dart
index 0937f311b6473a0be29e42fcb270b9cbd7f2e795..b148dcfcf643995fd38926b69805e95783ee3a83 100644
--- a/dart/lib/compiler/implementation/scanner/listener.dart
+++ b/dart/lib/compiler/implementation/scanner/listener.dart
@@ -9,6 +9,12 @@ const bool VERBOSE = false;
  * on parser errors.
  */
 class Listener {
+  void beginArgumentDefinitionTest(Token token) {
+  }
+
+  void endArgumentDefinitionTest(Token beginToken, Token endToken) {
+  }
+
   void beginArguments(Token token) {
   }
 
@@ -932,6 +938,10 @@ class NodeListener extends ElementListener {
   NodeListener(DiagnosticListener listener, CompilationUnitElement element)
     : super(listener, element, null);
 
+  void endArgumentDefinitionTest(Token beginToken, Token endToken) {
+    pushNode(new Send.prefix(popNode(), new Operator(beginToken)));
+  }
+
   void endClassDeclaration(int interfacesCount, Token beginToken,
                            Token extendsKeyword, Token implementsKeyword,
                            Token endToken) {