src/vs/workbench/contrib/webview/browser/webviewElement.ts/WebviewElement/_webviewContentOrigin
class WebviewElement:	private _webviewContentOrigin(encodedWebviewOrigin: string): string {
		const uri = URI.parse(this.webviewContentEndpoint(encodedWebviewOrigin));
		return uri.scheme + '://' + uri.authority.toLowerCase();
	}