Move embedder locator and convert context builder to use the new API

pkg/analyzer/lib/src/dart/sdk/sdk.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.src.generated.sdk2;
 
 import 'dart:collection';
 import 'dart:io' as io;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 101 matching lines @@
    * Specify whether SDK summary should be used.
    */
   void set useSummary(bool use) {
     if (_analysisContext != null) {
       throw new StateError(
           'The "useSummary" flag cannot be changed after context creation.');
     }
     _useSummary = use;
   }
 
+  /**
+   * Add the extensions from one or more sdk extension files to this sdk. The
+   * [extensions] should be a table mapping the names of extensions to the paths
+   * where those extensions can be found.
+   */
+  void addExtensions(Map<String, String> extensions) {
+    extensions.forEach((String uri, String path) {
+      String shortName = uri.substring(uri.indexOf(':') + 1);
+      SdkLibraryImpl library = new SdkLibraryImpl(shortName);
+      library.path = path;
+      libraryMap.setLibrary(uri, library);
+    });
+  }
+
   @override
   Source fromFileUri(Uri uri) {
     File file =
         resourceProvider.getFile(resourceProvider.pathContext.fromUri(uri));
     String path = _getPath(file);
     if (path == null) {
       return null;
     }
     try {
       return file.createSource(parseUriWithException(path));
@@ skipping 567 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;
   }
 }