Enhance ClassNode prettyprint

lib/compiler/implementation/tree/prettyprint.dart

Index: lib/compiler/implementation/tree/prettyprint.dart
diff --git a/lib/compiler/implementation/tree/prettyprint.dart b/lib/compiler/implementation/tree/prettyprint.dart
index 7ba611d12324982e2346510855c7b4c5c6d533f3..31b272487da592c7b9f4efcaef802d2b21dca816 100644
--- a/lib/compiler/implementation/tree/prettyprint.dart
+++ b/lib/compiler/implementation/tree/prettyprint.dart
@@ -127,7 +127,17 @@ class PrettyPrinter implements Visitor {
   }
 
   visitClassNode(ClassNode node) {
-    visitNodeWithChildren(node, "ClassNode");
+    openNode("ClassNode", {
+      "beginToken" : tokenToStringOrNull(node.getBeginToken()),
+      "endToken" : tokenToStringOrNull(node.getEndToken()),
+      "extendsKeyword" : tokenToStringOrNull(node.extendsKeyword),
+    });
+    visitWithPrefix(node.name, "name:");
+    visitWithPrefix(node.superclass, "superclass:");
+    visitWithPrefix(node.interfaces, "interfaces:");
+    visitWithPrefix(node.typeParameters, "typeParameters:");
+    visitWithPrefix(node.defaultClause, "defaultClause:");
+    closeNode("ClassNode");
   }
 
   visitConditional(Conditional node) {