Replace 'length' with more generic 'extractProperty' operation.

pkg/analyzer/test/src/summary/summarize_elements_test.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 analyzer.test.src.summary.summarize_elements_test;
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/source_io.dart';
@@ skipping 46 matching lines @@
   /**
    * Determine the analysis options that should be used for this test.
    */
   AnalysisOptionsImpl get options =>
       new AnalysisOptionsImpl()..enableGenericMethods = true;
 
   @override
   bool get skipFullyLinkedData => false;
 
   @override
+  bool get skipNonConstInitializers => true;
+
+  @override
   bool get strongMode => false;
 
   @override
   Source addNamedSource(String filePath, String contents) {
     Source source = super.addNamedSource(filePath, contents);
     _fileContents[source] = contents;
     return source;
   }
 
   /**
@@ skipping 71 matching lines @@
       } else {
         UnlinkedPublicNamespace namespace =
             computePublicNamespaceFromText(text, source);
         expect(canonicalize(namespace),
             canonicalize(unlinkedUnits[i].publicNamespace),
             reason: 'publicNamespace(${unitUris[i]})');
       }
     }
   }
 }