Add DirectoryBasedDartSdk.useSummary property.

pkg/analyzer/tool/summary/build_sdk_summaries.dart

 import 'dart:io';
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_io.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/sdk_io.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/summary/format.dart';
 import 'package:analyzer/src/summary/summarize_elements.dart';
@@ skipping 69 matching lines @@
    * Build a strong or spec mode summary for the Dart SDK at [sdkPath].
    */
   void build() {
     print('Generating ${strongMode ? 'strong' : 'spec'} mode summary.');
     Stopwatch sw = new Stopwatch()..start();
     //
     // Prepare SDK.
     //
     DirectoryBasedDartSdk sdk =
         new DirectoryBasedDartSdk(new JavaFile(sdkPath));
+    sdk.useSummary = false;
     context = sdk.context;
     context.analysisOptions = new AnalysisOptionsImpl()
       ..strongMode = strongMode;
     //
     // Serialize each SDK library.
     //
     for (SdkLibrary lib in sdk.sdkLibraries) {
       Source libSource = sdk.mapDartUri(lib.shortName);
       _serializeLibrary(libSource);
     }
@@ skipping 35 matching lines @@
   void _serializeSingleLibrary(LibraryElement element) {
     String uri = element.source.uri.toString();
     LibrarySerializationResult libraryResult =
         serializeLibrary(element, context.typeProvider, strongMode);
     linkedLibraryUris.add(uri);
     linkedLibraries.add(libraryResult.linked);
     unlinkedUnitUris.addAll(libraryResult.unitUris);
     unlinkedUnits.addAll(libraryResult.unlinkedUnits);
   }
 }