Reapply "Add "load from .dill" file capability and run a white-box test.""

pkg/compiler/lib/src/js_backend/mirrors_analysis.dart

 // Copyright (c) 2016, 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.mirrors_handler;
 
 import '../common.dart';
 import '../common/resolution.dart';
 import '../compiler.dart';
 import '../constants/values.dart';
@@ skipping 102 matching lines @@
       // necessary, but the backend relies on them being resolved.
       enqueuer.applyImpact(
           _computeImpactForReflectiveStaticFields(_findStaticFieldTargets()));
     }
 
     if (_mirrorsData.mustPreserveNames) _reporter.log('Preserving names.');
 
     if (_mirrorsData.mustRetainMetadata) {
       _reporter.log('Retaining metadata.');
 
-      _compiler.libraryLoader.libraries.forEach(_mirrorsData.retainMetadataOf);
+      (_compiler.libraryLoader.libraries as Iterable<LibraryElement>)
+          .forEach(_mirrorsData.retainMetadataOf);
 
       if (!enqueuer.queueIsClosed) {
         /// Register the constant value of [metadata] as live in resolution.
         void registerMetadataConstant(MetadataAnnotation metadata) {
           ConstantValue constant =
               _constants.getConstantValueForMetadata(metadata);
           Dependency dependency =
               new Dependency(constant, metadata.annotatedElement);
           _metadataConstants.add(dependency);
           _impactBuilder.registerConstantUse(new ConstantUse.mirrors(constant));
@@ skipping 102 matching lines @@
     if (_mirrorsData.isTreeShakingDisabled) {
       enqueuer.applyImpact(_computeImpactForReflectiveElements(recentClasses,
           enqueuer.processedClasses, _compiler.libraryLoader.libraries));
     }
 
     if (_mirrorsData.mustPreserveNames) _reporter.log('Preserving names.');
 
     if (_mirrorsData.mustRetainMetadata) {
       _reporter.log('Retaining metadata.');
 
-      _compiler.libraryLoader.libraries.forEach(_mirrorsData.retainMetadataOf);
+      (_compiler.libraryLoader.libraries as Iterable<LibraryElement>)
+          .forEach(_mirrorsData.retainMetadataOf);
 
       for (Dependency dependency in _metadataConstants) {
         _impactBuilder
             .registerConstantUse(new ConstantUse.mirrors(dependency.constant));
       }
       _metadataConstants.clear();
       enqueuer.applyImpact(_impactBuilder.flush());
     }
   }
 }
@@ skipping 211 matching lines @@
 
 /// Records that [constant] is used by the element behind [registry].
 class Dependency {
   final ConstantValue constant;
   final Element annotatedElement;
 
   const Dependency(this.constant, this.annotatedElement);
 
   String toString() => '$annotatedElement:${constant.toStructuredText()}';
 }