Fix more errors in DDC SDK.

pkg/dev_compiler/tool/input_sdk/private/isolate_helper.dart

 // Copyright (c) 2012, 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 dart._isolate_helper;
 
 import 'dart:_js_embedded_names'
     show
         CLASS_ID_EXTRACTOR,
         CLASS_FIELDS_EXTRACTOR,
@@ skipping 728 matching lines @@
   // primitives that require support for spawning workers. The field starts out
   // by being null, and dart2js' type inference will track if it can have a
   // non-null value. So by testing if this value is not null, we generate code
   // that dart2js knows is dead when worker support isn't needed.
   // TODO(herhut): Initialize this to false when able to track compile-time
   // constants.
   static var enableSpawnWorker;
 
   static String thisScript = computeThisScript();
 
+  /// Returns the base path added to Uri.base to resolve `package:` Uris.
+  ///
+  /// This is used by `Isolate.resolvePackageUri` to load resources. The default
+  /// value is `packages/` but users can override this by using the
+  /// `defaultPackagesBase` hook.
+  static String get packagesBase =>
+      JS('String', r'#.defaultPackagesBase || "packages/"', global);
+
   /// Associates an ID with a native worker object.
   static final Expando<int> workerIds = new Expando<int>();
 
   /**
    * The src url for the script tag that loaded this Used to create
    * JavaScript workers.
    */
   static String computeThisScript() {
     // See: https://github.com/dart-lang/dev_compiler/issues/164
     // var currentScript = JS_EMBEDDED_GLOBAL('', CURRENT_SCRIPT);
@@ skipping 692 matching lines @@
   }
 
   bool operator ==(Object other) {
     if (identical(other, this)) return true;
     if (other is CapabilityImpl) {
       return identical(_id, other._id);
     }
     return false;
   }
 }