Fix create-property.js

[stonechoe]

This PR is for https://github.com/zloirock/core-js/issues/1322

The changes are as follows

module.exports = function (object, key, value) {
  var propertyKey = toPropertyKey(key);
  if (propertyKey in object) definePropertyModule.f(object, propertyKey, createPropertyDescriptor(0, value));
  else object[propertyKey] = value;
};

module.exports = function (object, key, value) {
  var propertyKey = toPropertyKey(key);
  definePropertyModule.f(object, propertyKey, createPropertyDescriptor(0, value));
};

I am not certain about the impact of this patch on performance - in case the existing code was intentionally written for performance benefits like JIT optimization, please handle it appropriately at your discretion.

[zloirock]

This PR should be to master branch.

You are right, it's a performance optimization. Without this optimization, some methods worked unacceptably slow. However, now most methods where it's used are available in most engines, and Proxy is enough popular. I will think make it sense to accept it or not.

[stonechoe]

Sorry for the confusion. I changed the base branch to master.

[stonechoe]

Thank you for your hard work for maintaining this project. May I ask a question?

Does the "unacceptable slowness" come from the fact that Object.defineProperty(object, key, createPropertyDescriptor(0, value)) cannot be optimized by engine, whereas object[key] = value can? Or does it only occur when polyfill version is used for definePropertyModule.f?

[zloirock]

Does the "unacceptable slowness" come from the fact that Object.defineProperty(object, key, createPropertyDescriptor(0, value)) cannot be optimized by engine, whereas object[key] = value can?

Yes. Some years ago it was dozens of times slower even in modern engines. I remember issues about optimizing this case in bug trackers of some engines. I didn't check the performance recently, so I don't know how it works in actual versions.