Migrate test block 9 to Dart 2.0

tests/corelib/hashcode_test.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.
-
-import "package:expect/expect.dart";
-
-class Override {
-  int hash;
-  int get superHash => super.hashCode;
-  int get hashCode => hash;
-
-  int foo() => hash; //   Just some function that can be closurized.
-
-  bool operator ==(Object other) =>
-      other is Override && (other as Override).hash == hash;
-}
-
-int bar() => 42; // Some global function.
-
-main() {
-  var o = new Object();
-  var hash = o.hashCode;
-  // Doesn't change.
-  Expect.equals(hash, o.hashCode);
-  Expect.equals(hash, identityHashCode(o));
-
-  var c = new Override();
-  int identityHash = c.superHash;
-  hash = (identityHash == 42) ? 37 : 42;
-  c.hash = hash;
-  Expect.equals(hash, c.hashCode);
-  Expect.equals(identityHash, identityHashCode(c));
-
-  // These classes don't override hashCode.
-  var samples = [0, 0x10000000, 1.5, -0, null, true, false, const Object()];
-  for (var v in samples) {
-    print(v);
-    Expect.equals(v.hashCode, identityHashCode(v));
-  }
-  // These do, or might do, but we can still use hashCodeOf and get the same
-  // result each time.
-  samples = ["string", "", (x) => 42, c.foo, bar];
-  for (var v in samples) {
-    print(v);
-    Expect.equals(v.hashCode, v.hashCode);
-    Expect.equals(identityHashCode(v), identityHashCode(v));
-  }
-}