Add support for superSend to the new IR and dart backend.

sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree_printer.dart

 // Copyright (c) 2014, 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 dart_tree_printer;
 
 import 'dart_printer.dart';
 import '../tree/tree.dart' as tree;
 import '../scanner/scannerlib.dart';
 import '../util/util.dart';
@@ skipping 480 matching lines @@
       precedence = PRIMARY;
       result = new tree.LiteralSymbol(
           hash,
           makeList('.', exp.id.split('.').map(makeIdentifier)));
     } else if (exp is StringConcat) {
       precedence = PRIMARY;
       result = unparseStringLiteral(exp);
     } else if (exp is This) {
       precedence = CALLEE;
       result = makeIdentifier('this');
+    } else if (exp is Super) {
+      precedence = CALLEE;
+      result = makeIdentifier('super');
     } else if (exp is Throw) {
       precedence = EXPRESSION; // ???
       result = new tree.Throw(
           makeExpression(exp.expression),
           throwToken,
           throwToken); // endToken not used by unparser
     } else if (exp is TypeOperator) {
       precedence = RELATIONAL;
       tree.Operator operator;
       tree.Node rightOperand = makeType(exp.type);
@@ skipping 481 matching lines @@
             printStringChunk(chunk.previous),
             node);
       } else {
         return node;
       }
     }
     return printStringChunk(output.chunk);
   }
 
 }