Inline the has module

factoryWithTypeCheckers.js

@@ -12,6 +12,7 @@ var assign = require('object-assign');
 var ReactPropTypesSecret = require('./lib/ReactPropTypesSecret');
 var checkPropTypes = require('./checkPropTypes');
 
+var has = Function.call.bind(Object.prototype.hasOwnProperty);
 var printWarning = function() {};
 
 if (process.env.NODE_ENV !== 'production') {
@@ -318,7 +319,7 @@ module.exports = function(isValidElement, throwOnDirectAccess) {
         return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of type ' + ('`' + propType + '` supplied to `' + componentName + '`, expected an object.'));
       }
       for (var key in propValue) {
-        if (Object.prototype.hasOwnProperty.call(propValue, key)) {
+        if (has(propValue, key)) {
           var error = typeChecker(propValue, key, componentName, location, propFullName + '.' + key, ReactPropTypesSecret);
           if (error instanceof Error) {
             return error;