Add typedef AST node boilerplate.

pkg/kernel/lib/canonical_name.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 library kernel.canonical_name;
 
 import 'ast.dart';
 
 /// A string sequence that identifies a library, class, or member.
 ///
 /// Canonical names are organized in a prefix tree.  Each node knows its
@@ skipping 86 matching lines @@
     return name.isPrivate
         ? getChildFromUri(name.library.importUri).getChild(name.name)
         : getChild(name.name);
   }
 
   CanonicalName getChildFromMember(Member member) {
     return getChild(getMemberQualifier(member))
         .getChildFromQualifiedName(member.name);
   }
 
+  CanonicalName getChildFromTypedef(Typedef typedef_) {
+    return getChild('@typedefs').getChild(typedef_.name);
+  }
+
   void bindTo(Reference target) {
     if (reference == target) return;
     if (reference != null) {
       throw '$this is already bound';
     }
     if (target.canonicalName != null) {
       throw 'Cannot bind $this to ${target.node}, target is already bound to '
           '${target.canonicalName}';
     }
     target.canonicalName = this;
@@ skipping 29 matching lines @@
     }
     if (member is Field) {
       return '@fields';
     }
     if (member is Constructor) {
       return '@constructors';
     }
     throw 'Unexpected member: $member';
   }
 }