Use the explicit string 'dynamic' to refer to dynamic in summaries.

pkg/analyzer/lib/src/summary/resynthesize.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 summary_resynthesizer;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
@@ skipping 969 matching lines @@
         name = referenceResolution.name;
       }
       ElementLocationImpl location;
       if (referenceResolution.dependency != 0) {
         location = getReferencedLocation(
             linkedLibrary.dependencies[referenceResolution.dependency],
             referenceResolution.unit,
             name);
       } else if (referenceResolution.kind == ReferenceKind.unresolved) {
         return summaryResynthesizer.typeProvider.undefinedType;
-      } else if (name.isEmpty) {
+      } else if (name == 'dynamic') {
         return summaryResynthesizer.typeProvider.dynamicType;
       } else {
         String referencedLibraryUri = librarySource.uri.toString();
         String partUri;
         if (referenceResolution.unit != 0) {
           String uri = unlinkedUnits[0].publicNamespace.parts[
               referenceResolution.unit - 1];
           Source partSource =
               summaryResynthesizer.sourceFactory.resolveUri(librarySource, uri);
           partUri = partSource.uri.toString();
@@ skipping 206 matching lines @@
     for (PropertyAccessorElementImpl accessor in unit.accessors) {
       elementMap[accessor.identifier] = accessor;
     }
     resummarizedElements[absoluteUri] = elementMap;
     unitHolder = null;
     linkedUnit = null;
     unlinkedUnit = null;
     linkedTypeMap = null;
   }
 }