Additional received WebMessage objects. To pass additionalObjects via WebMessage to the app, use the chrome.webview.postMessageWithAdditionalObjects content API. Any DOM object type that can be natively representable that has been passed in to additionalObjects parameter will be accessible here. Currently a WebMessage object can be the ICoreWebView2File type. Entries in the collection can be nullptr if null or undefined was passed.
The URI of the document that sent this web message.
The message posted from the WebView content to the host converted to a JSON string. Run this operation to communicate using JavaScript objects.
If the message posted from the WebView content to the host is a string type, this method returns the value of that string. If the message posted is some other kind of JavaScript type this method fails with the following error.