Stop using the Hashable interface.

tests/language/savannah_test.dart

 // Copyright (c) 2011, 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.
 // Dart test using an identity hash.
 
-abstract class BigGame extends Hashable {
+abstract class BigGame {
   String get name;
 }
 
 // Giraffe overrides hashCode and provides its own identity hash.
 class Giraffe implements BigGame {
   final String name;
   final int identityHash_;
 
   Giraffe(this.name) : identityHash_ = nextId() {}
 
@@ skipping 11 matching lines @@
   }
 }
 
 // Zebra relies on the system provided identity hash.
 class Zebra implements BigGame {
   final String name;
   Zebra(this.name) {}
 }
 
 
-class SavannahTest  {
+class SavannahTest {
 
   static void testMain() {
     Map<BigGame, String> savannah = new Map<BigGame, String>();
 
     Giraffe giraffe1 = new Giraffe("Tony");
     Giraffe giraffe2 = new Giraffe("Rose");
     savannah[giraffe1] = giraffe1.name;
     savannah[giraffe2] = giraffe2.name;
     print("giraffe1 hash: ${giraffe1.hashCode()}");
     print("giraffe2 hash: ${giraffe2.hashCode()}");
@@ skipping 22 matching lines @@
     print("zebra2: ${savannah[zebra2]}");
     Expect.equals("Paolo", savannah[zebra1]);
     Expect.equals("Zeeta", savannah[zebra2]);
   }
 
 }
 
 main() {
   SavannahTest.testMain();
 }