Add typedef AST node boilerplate.

runtime/vm/kernel.cc

Index: runtime/vm/kernel.cc
diff --git a/runtime/vm/kernel.cc b/runtime/vm/kernel.cc
index 135609ec0b0b50b39f553ef216f0a57d07d326d7..4ec55e15245656dbce9c2c0ddd7c8fce096b3c06 100644
--- a/runtime/vm/kernel.cc
+++ b/runtime/vm/kernel.cc
@@ -84,6 +84,20 @@ void Library::VisitChildren(Visitor* visitor) {
 }
 
 
+Typedef::~Typedef() {}
+
+
+void Typedef::AcceptTreeVisitor(TreeVisitor* visitor) {
+  visitor->VisitTypedef(this);
+}
+
+
+void Typedef::VisitChildren(Visitor* visitor) {
+  VisitList(&type_parameters(), visitor);
+  type()->AcceptDartTypeVisitor(visitor);
+}
+
+
 Class::~Class() {}
 
 
@@ -1192,6 +1206,19 @@ void InterfaceType::VisitChildren(Visitor* visitor) {
 }
 
 
+TypedefType::~TypedefType() {}
+
+
+void TypedefType::AcceptDartTypeVisitor(DartTypeVisitor* visitor) {
+  visitor->VisitTypedefType(this);
+}
+
+
+void TypedefType::VisitChildren(Visitor* visitor) {
+  VisitList(&type_arguments(), visitor);
+}
+
+
 FunctionType::~FunctionType() {}