Add interfaces for a new compiler API.

tests/compiler/dart2js/sourcemaps/sourcemap_helper.dart

 // Copyright (c) 2015, 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 sourcemap.helper;
 
 import 'dart:async';
+import 'package:compiler/compiler_new.dart';
 import 'package:compiler/src/apiimpl.dart' as api;
-import 'package:compiler/src/dart2jslib.dart' show NullSink;
+import 'package:compiler/src/null_compiler_output.dart' show NullSink;
 import 'package:compiler/src/elements/elements.dart';
 import 'package:compiler/src/helpers/helpers.dart';
 import 'package:compiler/src/filenames.dart';
 import 'package:compiler/src/io/source_file.dart';
 import 'package:compiler/src/io/source_information.dart';
 import 'package:compiler/src/js/js.dart' as js;
 import 'package:compiler/src/js/js_debug.dart';
 import 'package:compiler/src/js/js_source_mapping.dart';
 import 'package:compiler/src/js_backend/js_backend.dart';
 import 'package:compiler/src/source_file_provider.dart';
 import '../memory_compiler.dart';
 import '../output_collector.dart';
 
-class OutputProvider {
+class OutputProvider implements CompilerOutput {
   BufferedEventSink jsMapOutput;
 
-  EventSink<String> call(String name, String extension) {
+  @override
+  EventSink<String> createEventSink(String name, String extension) {
     if (extension == 'js.map') {
       return jsMapOutput = new BufferedEventSink();
     }
     return new NullSink('$name.$extension');
   }
 }
 
 class CloningOutputProvider extends OutputProvider {
   RandomAccessFileOutputProvider outputProvider;
 
   CloningOutputProvider(Uri jsUri, Uri jsMapUri)
     : outputProvider = new RandomAccessFileOutputProvider(jsUri, jsMapUri);
 
-  EventSink<String> call(String name, String extension) {
+  @override
+  EventSink<String> createEventSink(String name, String extension) {
     EventSink<String> output = outputProvider(name, extension);
     if (extension == 'js.map') {
       output = new CloningEventSink(
           [output, jsMapOutput = new BufferedEventSink()]);
     }
     return output;
   }
 }
 
 abstract class SourceFileManager {
@@ skipping 275 matching lines @@
       this.jsCode,
       this.sourceLocation,
       this.dartCode,
       {this.isMissing: false});
 
   String toString() {
     return 'CodePoint[kind=$kind,js=$jsCode,dart=$dartCode,'
                      'location=$sourceLocation]';
   }
 }