Add interfaces for a new compiler API.

tests/compiler/dart2js/bad_output_io_test.dart

 // Copyright (c) 2013, 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.
 
 // Test that the compiler can handle imports when package root has not been set.
 
 library dart2js.test.missing_file;
 
 import 'dart:io' show exit;
 import 'package:expect/expect.dart';
@@ skipping 19 matching lines @@
 
   final int FATAL = 0;
   final int INFO = 1;
 
   final messages = [];
 
   void info(var message, [kind]) {
    messages.add([message, kind]);
   }
 
-  void diagnosticHandler(Uri uri, int begin, int end, String message, kind) {
+  @override
+  void report(Uri uri, int begin, int end, String message, kind) {
     messages.add([message, kind]);
   }
 
+  @override
   void call(Uri uri, int begin, int end, String message, kind) {
-    diagnosticHandler(uri, begin, end, message, kind);
+    report(uri, begin, end, message, kind);
   }
 
   String prefixMessage(String message, Diagnostic kind) {
     return message;
   }
 
   int fatalCount;
 
   int throwOnErrorCount;
 }
@@ skipping 11 matching lines @@
     CollectingFormattingDiagnosticHandler handler = diagnosticHandler;
     Expect.equals(1, handler.messages.length);
     var message = handler.messages[0];
     Expect.isTrue(message[0].contains("Cannot open file"));
     Expect.equals(Diagnostic.ERROR, message[1]);
     Expect.equals(1, exitCode);
     exit(0);
   };
   compile(["foo.dart", "--out=bar.dart"]);
 }