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

pkg/compiler/lib/src/js_emitter/full_emitter/emitter.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 dart2js.js_emitter.full_emitter;
 
 import 'dart:collection' show HashMap;
 import 'dart:convert';
 
 import 'package:js_runtime/shared/embedded_names.dart' as embeddedNames;
@@ skipping 402 matching lines @@
             generateEmbeddedGlobalAccessString(embeddedNames.GLOBAL_FUNCTIONS);
         return jsAst.js.expressionTemplateFor("$functionGettersMap[#]()");
 
       default:
         reporter.internalError(
             NO_LOCATION_SPANNABLE, "Unhandled Builtin: $builtin");
         return null;
     }
   }
 
+  @override
+  int generatedSize(OutputUnit unit) {
+    return outputBuffers[unit].length;
+  }
+
   List<jsAst.Statement> buildTrivialNsmHandlers() {
     return nsmEmitter.buildTrivialNsmHandlers();
   }
 
   jsAst.Statement buildNativeInfoHandler(
       jsAst.Expression infoAccess,
       jsAst.Expression constructorAccess,
       jsAst.Expression subclassReadGenerator(jsAst.Expression subclass),
       jsAst.Expression interceptorsByTagAccess,
       jsAst.Expression leafTagsAccess) {
@@ skipping 1746 matching lines @@
     if (cachedElements.isEmpty) return;
     for (Element element in backend.codegenEnqueuer.newlyEnqueuedElements) {
       if (element.isInstanceMember) {
         cachedClassBuilders.remove(element.enclosingClass);
 
         nativeEmitter.cachedBuilders.remove(element.enclosingClass);
       }
     }
   }
 }