[intl] Remove redundant type checking system

src/js/i18n.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // ECMAScript 402 API implementation.
 
 /**
  * Intl object is a single object that has some named properties,
  * all of which are constructors.
  */
@@ skipping 1729 matching lines @@
 
   return %InternalDateFormat(%GetImplFromInitializedIntlObject(formatter),
                              new GlobalDate(dateMs));
 }
 
 function FormatDateToParts(dateValue) {
   CHECK_OBJECT_COERCIBLE(this, "Intl.DateTimeFormat.prototype.formatToParts");
   if (!IS_OBJECT(this)) {
     throw %make_type_error(kCalledOnNonObject, this);
   }
+  if (!%IsInitializedIntlObjectOfType(this, 'dateformat')) {
+    throw %make_type_error(kIncompatibleMethodReceiver,
+                          'Intl.DateTimeFormat.prototype.formatToParts',
+                          this);
+  }
   var dateMs;
   if (IS_UNDEFINED(dateValue)) {
     dateMs = %DateCurrentTime();
   } else {
     dateMs = TO_NUMBER(dateValue);
   }
 
   if (!NUMBER_IS_FINITE(dateMs)) throw %make_range_error(kDateRange);
 
   return %InternalDateFormatToParts(
@@ skipping 437 matching lines @@
   }
 );
 
 %FunctionRemovePrototype(FormatDateToParts);
 
 utils.Export(function(to) {
   to.FormatDateToParts = FormatDateToParts;
 });
 
 })