Get's the base URL for this instance of the Snippet Preview.

@private
@this SnippetPreview

@returns {string} The base URL.
function() {
	var baseURL = this.opts.baseURL;

	/*
	 * For backwards compatibility, if no URL was passed to the snippet editor we try to retrieve the base URL from the
	 * rawData in the App. This is because the scrapers used to be responsible for retrieving the baseURL, but the base
	 * URL is static so we can just pass it to the snippet editor.
	 */
	if ( this.hasApp() && ! isEmpty( this.refObj.rawData.baseUrl ) && this.opts.baseURL === defaults.baseURL ) {
		baseURL = this.refObj.rawData.baseUrl;
	}

	return baseURL;
}