use webContents.openDevTools

https://github.com/atom/electron/issues/3125#issuecomment-148975593

docs/tutorial/quick-start.md

@@ -107,7 +107,7 @@ app.on('ready', function() {
   mainWindow.loadUrl('file://' + __dirname + '/index.html');
 
   // Open the DevTools.
-  mainWindow.openDevTools();
+  mainWindow.webContents.openDevTools();
 
   // Emitted when the window is closed.
   mainWindow.on('closed', function() {