Make Dart_IdentityEqual live up to its sepc and not leak boxing implementation detail. (Reland r275…

runtime/lib/identical.cc

 // 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.
 
 #include "vm/bootstrap_natives.h"
 
 #include "vm/object.h"
 
 namespace dart {
 
 DEFINE_NATIVE_ENTRY(Identical_comparison, 2) {
   GET_NATIVE_ARGUMENT(Instance, a, arguments->NativeArgAt(0));
   GET_NATIVE_ARGUMENT(Instance, b, arguments->NativeArgAt(1));
-  if (a.raw() == b.raw()) return Bool::True().raw();
-  if (a.IsInteger() && b.IsInteger()) {
-    return Bool::Get(a.Equals(b)).raw();
-  }
-  if (a.IsDouble() && b.IsDouble()) {
-    if (a.Equals(b)) return Bool::True().raw();
-    // Check for NaN.
-    const Double& a_double = Double::Cast(a);
-    const Double& b_double = Double::Cast(b);
-    if (isnan(a_double.value()) && isnan(b_double.value())) {
-      return Bool::True().raw();
-    }
-  }
-  return Bool::False().raw();
+  return Bool::Get(a.IsIdenticalTo(b)).raw();
 }
 
-
 }  // namespace dart