Don't add sources to DartSdk contexts.

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/dart/ast/ast.dart';
@@ skipping 240 matching lines @@
     this._sdkDirectory = sdkDirectory.getAbsoluteFile();
     _libraryMap = initialLibraryMap(useDart2jsPaths);
   }
 
   @override
   AnalysisContext get context {
     if (_analysisContext == null) {
       _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.resultProvider =
             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;
   }
 
   /**
    * Return the file containing the dart2js executable, or `null` if it does not
    * exist.
    */
   JavaFile get dart2JsExecutable {
     if (_dart2jsExecutable == null) {
@@ skipping 367 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;
   }
 }