Fix dart2js hashCode implementations.

tests/compiler/dart2js_extra/hash_code_test.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.
 
-// dart2js specific test to make sure String.hashCode behaves as
+// dart2js specific test to make sure hashCode on intercepted types behaves as
 // intended.
 
+
+class Hasher {
+  confuse(x) => [1, 'x', true, null, x].last;
+  hash(x) => confuse(x).hashCode;
+}
+
+// Hashing via [hash] should be forced to use the general interceptor, but the
+// local x.hashCode calls might be optimized.
+var hash = new Hasher().hash;
+
+check(value1, value2) {
+  var h1 = hash(value1);
+  var h2 = hash(value2);
+
+  Expect.isTrue(h1 is int);
+  Expect.isTrue(h2 is int);
+  Expect.isFalse(h1 == h2);
+
+  // We expect that the hash function is reasonable quality - there are some
+  // difference in the low bits.
+  Expect.isFalse((h1 & 0xf) == (h2 & 0xf));
+
+  // Quality check - the values should be SMIs for efficient arithmetic.
+  Expect.equals((h1 & 0x1fffffff), h1);
+  Expect.equals((h2 & 0x1fffffff), h2);
+}
+
+bools() {
+  check(true, false);
+
+  Expect.equals(true.hashCode, hash(true));   // First can be optimized.
+  Expect.equals(false.hashCode, hash(false));
+}
+
+ints() {
+  var i1 = 100;
+  var i2 = 101;
+  check(i1, i2);
+  Expect.equals(i1.hashCode, hash(i1));
+  Expect.equals(i2.hashCode, hash(i2));
+}
+
+lists() {
+  var list1 = [];
+  var list2 = [];
+  check(list1, list2);
+
+  Expect.equals(list1.hashCode, hash(list1));
+  Expect.equals(list2.hashCode, hash(list2));
+}
+
+strings() {
+  var str1 = 'a';
+  var str2 = 'b';
+  var str3 = 'c';
+  check(str1, str2);
+  check(str1, str3);
+  check(str2, str3);
+
+  Expect.equals(str1.hashCode, hash(str1));
+  Expect.equals(str2.hashCode, hash(str2));
+  Expect.equals(str3.hashCode, hash(str3));
+
+  Expect.equals(0xA2E9442, 'a'.hashCode);
+  Expect.equals(0x0DB819B, 'b'.hashCode);
+  Expect.equals(0xEBA5D59, 'c'.hashCode);
+}
+
 main() {
-  Expect.equals(67633152, 'a'.hashCode);
-  Expect.equals(37224448, 'b'.hashCode);
+  bools();
+  ints();
+  lists();
+  strings();
 }