deserializeWebviewPanel  
  abstract fun deserializeWebviewPanel(webviewPanel: WebviewPanel, state: T): PromiseLike<Void?>(source)
Restore a webview panel from its serialized state.
Called when a serialized webview first becomes visible.
Parameters
webviewPanel 
Webview panel to restore. The serializer should take ownership of this panel. The serializer must restore the webview's .html and hook up all webview events.
state
Persisted state from the webview content.