Add interfaces for a new compiler API.

tests/compiler/dart2js/deferred_custom_element_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 of the graph segmentation algorithm used by deferred loading
 // to determine which elements can be deferred and which libraries
 // much be included in the initial download (loaded eagerly).
 
+import 'package:async_helper/async_helper.dart';
+import 'package:compiler/src/dart2jslib.dart';
 import 'package:expect/expect.dart';
-import "package:async_helper/async_helper.dart";
-import 'memory_source_file_helper.dart';
-import "dart:async";
-
-class FakeOutputStream<T> extends EventSink<T> {
-  void add(T event) {}
-  void addError(T event, [StackTrace stackTrace]) {}
-  void close() {}
-}
+import 'memory_compiler.dart';
 
 void main() {
-  Uri script = currentDirectory.resolveUri(Platform.script);
-  Uri libraryRoot = script.resolve('../../../sdk/');
-  Uri packageRoot = script.resolve('./packages/');
-
-  var provider = new MemorySourceFileProvider(MEMORY_SOURCE_FILES);
-  var handler = new FormattingDiagnosticHandler(provider);
-
-  Compiler compiler = new Compiler(provider.readStringFromUri,
-                                   (name, extension) => new FakeOutputStream(),
-                                   handler.diagnosticHandler,
-                                   libraryRoot,
-                                   packageRoot,
-                                   [],
-                                   {});
+  Compiler compiler = compilerFor(MEMORY_SOURCE_FILES);
   asyncTest(() => compiler.run(Uri.parse('memory:main.dart')).then((_) {
     var outputUnitForElement = compiler.deferredLoadTask.outputUnitForElement;
     var mainOutputUnit = compiler.deferredLoadTask.mainOutputUnit;
     var lib =
         compiler.libraryLoader.lookupLibrary(Uri.parse("memory:lib.dart"));
     var customType = lib.find("CustomType");
     var foo = lib.find("foo");
     Expect.notEquals(mainOutputUnit, outputUnitForElement(foo));
     // Native elements are not deferred
     Expect.equals(mainOutputUnit, outputUnitForElement(customType));
@@ skipping 15 matching lines @@
 import 'dart:html';
 var a = CustomType;
 
 class CustomType extends HtmlElement {
   factory CustomType() => null;
   CustomType.created() : super.created() ;
 }
 
 foo() {}
 """,};