[builtins] Properly optimize Object.prototype.isPrototypeOf.

src/js/v8natives.js

Index: src/js/v8natives.js
diff --git a/src/js/v8natives.js b/src/js/v8natives.js
index 5ae75bae22e40118e82400c8ac107f36cc5356df..bac031fc57f910a454548d2bad9d619af0644bca 100644
--- a/src/js/v8natives.js
+++ b/src/js/v8natives.js
@@ -21,15 +21,6 @@ function ObjectToLocaleString() {
   return this.toString();
 }
 
-
-// ES6 19.1.3.3 Object.prototype.isPrototypeOf(V)
-function ObjectIsPrototypeOf(V) {
-  if (!IS_RECEIVER(V)) return false;
-  var O = TO_OBJECT(this);
-  return %HasInPrototypeChain(V, O);
-}
-
-
 // ES6 7.3.9
 function GetMethod(obj, p) {
   var func = obj[p];
@@ -62,7 +53,7 @@ utils.InstallFunctions(GlobalObject.prototype, DONT_ENUM, [
   // toString is added in bootstrapper.cc
   "toLocaleString", ObjectToLocaleString,
   // valueOf is added in bootstrapper.cc.
-  "isPrototypeOf", ObjectIsPrototypeOf,
+  // isPrototypeOf is added in bootstrapper.cc.
   // propertyIsEnumerable is added in bootstrapper.cc.
   // __defineGetter__ is added in bootstrapper.cc.
   // __lookupGetter__ is added in bootstrapper.cc.