Implement argument definition test in the vm.

runtime/vm/ast.h

Index: runtime/vm/ast.h
===================================================================
--- runtime/vm/ast.h	(revision 11663)
+++ runtime/vm/ast.h	(working copy)
@@ -32,6 +32,7 @@
   V(ForNode, "for")                                                            \
   V(JumpNode, "jump")                                                          \
   V(ArgumentListNode, "args")                                                  \
+  V(ArgumentDefinitionTestNode, "defined")                                     \
   V(ArrayNode, "array")                                                        \
   V(ClosureNode, "closure")                                                    \
   V(InstanceCallNode, "instance call")                                         \
@@ -244,6 +245,41 @@
 };
 
 
+class ArgumentDefinitionTestNode : public AstNode {
+ public:
+  ArgumentDefinitionTestNode(intptr_t token_pos,
+                             intptr_t formal_parameter_index,
+                             const String& formal_parameter_name,
+                             LocalVariable* saved_arguments_descriptor)
+     : AstNode(token_pos),
+       formal_parameter_index_(formal_parameter_index),
+       formal_parameter_name_(formal_parameter_name),
+       saved_arguments_descriptor_(*saved_arguments_descriptor) {
+    ASSERT(formal_parameter_index_ >= 0);
+    ASSERT(formal_parameter_name_.IsZoneHandle());
+    ASSERT(formal_parameter_name_.IsSymbol());
+    ASSERT(saved_arguments_descriptor != NULL);
+  }
+
+  virtual void VisitChildren(AstNodeVisitor* visitor) const { }
+
+  intptr_t formal_parameter_index() const { return formal_parameter_index_; }
+  const String& formal_parameter_name() const { return formal_parameter_name_; }
+  const LocalVariable& saved_arguments_descriptor() const {
+    return saved_arguments_descriptor_;
+  }
+
+  DECLARE_COMMON_NODE_FUNCTIONS(ArgumentDefinitionTestNode);
+
+ private:
+  const intptr_t formal_parameter_index_;
+  const String& formal_parameter_name_;
+  const LocalVariable& saved_arguments_descriptor_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArgumentDefinitionTestNode);
+};
+
+
 class ArrayNode : public AstNode {
  public:
   ArrayNode(intptr_t token_pos, const AbstractType& type)