WebUI fixes for SDK 0.8.10

lib/src/utils_observe.dart

 // Copyright (c) 2013, 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 web_ui.src.utils_observe;
 
-import 'dart:collection';
-
 // TODO(jmesserly): helpers to combine hash codes. Reuse these from somewhere.
 hash2(x, y) => x.hashCode * 31 + y.hashCode;
 
 hash3(x, y, z) => hash2(hash2(x, y), z);
 
 hash4(w, x, y, z) => hash2(hash2(w, x), hash2(y, z));
 
 class Arrays {
   static void copy(List src, int srcStart,
                    List dst, int dstStart, int count) {
@@ skipping 19 matching lines @@
     if (start < 0 ) {
       String message = "$start must be greater than or equal to 0";
       throw new RangeError(message);
     }
     if (start + length > a.length) {
       String message = "$start + $length must be in the range [0..${a.length})";
       throw new RangeError(message);
     }
   }
 }
-
-// TODO(jmesserly): bogus type to workaround spurious VM bug with generic base
-// class and mixins.
-abstract class IterableWorkaround extends IterableBase<dynamic> {}
-abstract class ListMixinWorkaround extends ListMixin<dynamic> {}