React Native WebView userAgent to use Chrome instead of Android stock browser

Using React Native, I am using the following WebView:

<WebView
  ref={webview => (this.webview = webview)}
  source={{
    uri: `${this.state.enviroment}`
  }}
  onMessage={this.onMessage}
  injectedJavaScript={patchPostMessageJsCode}
  style={{ backgroundColor: "black" }}
/>

This works, but the issue is that this uses the stock Android browser to load my page. This is a problem because on Android 4.1 in the stock browser, there are issues with the site.

Having said that, on the same OS version, the site is fine on Chrome.

How can I use the userAgent prop to tell my WebView to use Chrome to load the page instead of the stock browser?