Get rid of duplication of class node unparsing.

lib/compiler/implementation/tree/unparser.dart

 // Copyright (c) 2012, 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.
 
 // Returns null if no need to rename a node.
 typedef String Renamer(Node node);
 
 String unparse(Node node) {
   Unparser unparser = new Unparser();
   unparser.unparse(node);
@@ skipping 48 matching lines @@
   }
 
   visitCascade(Cascade node) {
     visit(node.expression);
   }
 
   visitCascadeReceiver(CascadeReceiver node) {
     visit(node.expression);
   }
 
-  visitClassNode(ClassNode node) {
+  unparseClassWithBody(ClassNode node, void classBodyEmitter()) {
     addToken(node.beginToken);
+    if (node.beginToken.stringValue == 'abstract') {
+      addToken(node.beginToken.next);
+    }
     visit(node.name);
     if (node.typeParameters !== null) {
       visit(node.typeParameters);
     }
-    sb.add(' ');
     if (node.extendsKeyword !== null) {
+      sb.add(' ');
       addToken(node.extendsKeyword);
       visit(node.superclass);
+    }
+    if (!node.interfaces.isEmpty()) {
       sb.add(' ');
+      visit(node.interfaces);
     }
-    visit(node.interfaces);
     if (node.defaultClause !== null) {
+      sb.add(' default ');
       visit(node.defaultClause);
-      sb.add(' ');
     }
-    sb.add('{\n');
-    NodeList body = node.body;
-    if (body !== null) {
-      Link nodes = body.nodes;
-      if (!nodes.isEmpty()) {
-        sb.add('  ');
-        nodes.printOn(sb, '\n  ');
+    sb.add('{');
+    classBodyEmitter();
+    sb.add('}');
+  }
+
+  visitClassNode(ClassNode node) {
+    unparseClassWithBody(node, () {
+      NodeList body = node.body;
+      if (body !== null) {
         sb.add('\n');
+        Link nodes = body.nodes;
+        if (!nodes.isEmpty()) {
+          sb.add('  ');
+          nodes.printOn(sb, '\n  ');
+          sb.add('\n');
+        }
       }
-    }
-    sb.add('}\n');
+    });
+    sb.add('\n');
   }
 
   visitConditional(Conditional node) {
     visit(node.condition);
     add(node.questionToken.value);
     visit(node.thenExpression);
     add(node.colonToken.value);
     visit(node.elseExpression);
   }
 
@@ skipping 397 matching lines @@
       sb.add(' ');
     }
     visit(node.name);
     if (node.typeParameters !== null) {
       visit(node.typeParameters);
     }
     visit(node.formals);
     add(node.endToken.value);
   }
 }