Add Object.hashCodeOf to get the default hashCode of an object.

sdk/lib/_internal/lib/core_patch.dart

Index: sdk/lib/_internal/lib/core_patch.dart
diff --git a/sdk/lib/_internal/lib/core_patch.dart b/sdk/lib/_internal/lib/core_patch.dart
index aaa816442dc320e3b21552d9f60f39a1e1f26b10..0a1c3ac8fac8c7ba09191e6340b08b572aa12cd1 100644
--- a/sdk/lib/_internal/lib/core_patch.dart
+++ b/sdk/lib/_internal/lib/core_patch.dart
@@ -30,6 +30,14 @@ patch void print(Object object) {
 patch class Object {
   patch int get hashCode => Primitives.objectHashCode(this);
 
+  patch static int hashCodeOf(Object object) {
+    // Basic JS non-object types don't work with objectHashCode.

[Johnni Winther, 2013/09/20 18:23:03]

Use the implementation for _objectHashCode in js_helper.dart instead.

[Lasse Reichstein Nielsen, 2013/09/23 07:08:28]

Done. Actually, I made _objectHashCode public in _jshelper, and call it directly
instead of copying the implementation.

I assume the "hashCode" implementation above is ok, because it only affects
non-primitive objects.

+    if (object is num || object is bool || object is String || object == null) {
+      return object.hashCode;
+    }
+    return Primitives.objectHashCode(object);
+  }
+
   patch String toString() => Primitives.objectToString(this);
 
   patch dynamic noSuchMethod(Invocation invocation) {