Unify handling of identical(NaN, NaN) between generated code and Dart API.

tests/language/number_identity2_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.
 // Dart test program for testing params.
 //
 // Contains test that is failing on dart2js. Merge this test with
 // 'number_identity_test.dart' once fixed.
 // VMOptions=--optimization-counter-threshold=10
 
 import "package:expect/expect.dart";
+import 'dart:typed_data';
 
-main() {
-  for (int i = 0; i < 20; i++) testNumberIdentity();
+double uint64toDouble(int i) {
+  var buffer = new Uint8List(8).buffer;
+  var bdata = new ByteData.view(buffer);
+  bdata.setUint64(0, i);
+  return bdata.getFloat64(0);
 }
 
-
 testNumberIdentity () {
   var a = double.NAN;
   var b = a + 0.0;
   Expect.isTrue(identical(a, b));
+
+  a = uint64toDouble((1 << 64) - 1);
+  b = uint64toDouble((1 << 64) - 2);
+  Expect.isFalse(identical(a, b));
+
+  a = 0.0/0.0;
+  b = 1.0/0.0;
+  Expect.isFalse(identical(a, b));
 }
+
+main() {
+  for (int i = 0; i < 20; i++) {
+    testNumberIdentity();
+  }
+}