Use togglefullscreen role which is now part of electron

https://github.com/electron/electron/pull/6166

src/main/menus/app.js

@@ -115,20 +115,7 @@ var createTemplate = function(mainWindow, config) {
         }
       }
     }, {
-      label: 'Toggle Full Screen',
+      role: 'togglefullscreen'
-      accelerator: (function() {
-        if (process.platform === 'darwin') {
-          return 'Ctrl+Command+F';
-        }
-        else {
-          return 'F11';
-        }
-      })(),
-      click: function(item, focusedWindow) {
-        if (focusedWindow) {
-          focusedWindow.setFullScreen(!focusedWindow.isFullScreen());
-        }
-      }
     }, separatorItem, {
       label: 'Actual Size',
       accelerator: 'CmdOrCtrl+0',