Prepare for chaining resynthesizers from AC to SDK AC.

pkg/analyzer/lib/src/generated/sdk_io.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 analyzer.src.generated.sdk_io;
 
 import 'dart:collection';
 import 'dart:io';
 
 import 'package:analyzer/src/context/context.dart';
@@ skipping 237 matching lines @@
    * should be used when it is available
    */
   DirectoryBasedDartSdk(JavaFile sdkDirectory, [bool useDart2jsPaths = false]) {
     this._sdkDirectory = sdkDirectory.getAbsoluteFile();
     _libraryMap = initialLibraryMap(useDart2jsPaths);
   }
 
   @override
   AnalysisContext get context {
     if (_analysisContext == null) {
-      SdkBundle sdkBundle = _getSummarySdkBundle();
-      if (sdkBundle != null) {
-        _analysisContext = new SummarySdkAnalysisContext(sdkBundle);
-      } else {
-        _analysisContext = new SdkAnalysisContext();
-      }
+      _analysisContext = new SdkAnalysisContext();
       SourceFactory factory = new SourceFactory([new DartUriResolver(this)]);
       _analysisContext.sourceFactory = factory;
       List<String> uris = this.uris;
+      // Try to use summaries.
+      SdkBundle sdkBundle = _getSummarySdkBundle();
+      if (sdkBundle != null) {
+        _analysisContext.aboutToComputeResultHelper =
+            new SdkSummaryResultProvider(_analysisContext, sdkBundle);
+      }
+      // Add sources.
       ChangeSet changeSet = new ChangeSet();
       for (String uri in uris) {
         changeSet.addedSource(factory.forUri(uri));
       }
       _analysisContext.applyChanges(changeSet);
     }
     return _analysisContext;
   }
 
   /**
@@ skipping 372 matching lines @@
     SdkLibrariesReader_LibraryBuilder libraryBuilder =
         new SdkLibrariesReader_LibraryBuilder(_useDart2jsPaths);
     // If any syntactic errors were found then don't try to visit the AST
     // structure.
     if (!errorListener.errorReported) {
       unit.accept(libraryBuilder);
     }
     return libraryBuilder.librariesMap;
   }
 }