Googlebot doesn't get Object.assign polyfilled

I ran into this issue that my React app wasn’t being rendered by Googlebot. By using Fetch as Google, I tracked it down to Object.assign not being available in Googlebot, even though I’m using the following polyfill:

https://cdn.polyfill.io/v2/polyfill.min.js?features=default

I tested this with the following code:

<h1>At what point do you stop working, Google?</h1>

{Object.assign && 'We have object.assign! :)'}
{!Object.assign && 'No object.assign available! :('}

Which renders the following in Fetch as Google:

Note that the left says “No object.assign available! 😦”.

[JakeChampion]

@williamoliveira We alias Googlebot to Chrome 41 😃 – https://github.com/Financial-Times/polyfill-service/blob/8ae2f6fa5b1a169aab01cad3b88bd577d67f8294/packages/polyfill-library/lib/UA.js#L145

[triblondon]

Currently we don’t support Googlebot as a browser family. We still recommend using the unknown=polyfill config parameter if you want to polyfill for search crawlers. We would welcome any efforts to either add and maintain a googlebot browser family, or create aliases to the appropriate versions of chrome or webkit. However, I’m aware that Google doesn’t publicly disclose which browser engine version is used by Googlebot, so it is kinda hard to do that.