enable --dump-info with the --fast-startup emitter

pkg/compiler/lib/src/compiler.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.
 
 library dart2js.compiler_base;
 
 import 'dart:async' show EventSink, Future;
 
 import '../compiler_new.dart' as api;
 import 'cache_strategy.dart' show CacheStrategy;
@@ skipping 212 matching lines @@
     // for global dependencies.
     globalDependencies = new GlobalDependencyRegistry();
 
     if (makeBackend != null) {
       backend = makeBackend(this);
     } else {
       backend = createBackend();
     }
     enqueuer = backend.makeEnqueuer();
 
-    if (options.dumpInfo && options.useStartupEmitter) {
-      throw new ArgumentError(
-          '--dump-info is not supported with the fast startup emitter');
-    }
-
     tasks = [
       dietParser = new DietParserTask(idGenerator, backend, reporter, measurer),
       scanner = createScannerTask(),
       serialization = new SerializationTask(this),
       libraryLoader = new LibraryLoaderTask(
           resolvedUriTranslator,
           options.compileOnly
               ? new _NoScriptLoader(this)
               : new _ScriptLoader(this),
           new _ElementScanner(scanner),
@@ skipping 1984 matching lines @@
   _ElementScanner(this.scanner);
   void scanLibrary(LibraryElement library) => scanner.scanLibrary(library);
   void scanUnit(CompilationUnitElement unit) => scanner.scan(unit);
 }
 
 class _EmptyEnvironment implements Environment {
   const _EmptyEnvironment();
 
   String valueOf(String key) => null;
 }