Just found one workaround to login Chat Mac App: Just change all the 'IN_NEW_WINDOW' and "EXTERNAL" to "_blank" in /Applications/Chat.app/Contents/Resources/app/main.js. Then start the Chat App and login, you can use the Chat App now.
Sorry, just found some issues when I do the changes on another employee's laptop. Not to replace all. I just open it with sublime and http prettify it. Then change 'IN_NEW_WINDOW' and "EXTERNAL" to "_blank" on line 2858, 2865 and 3058. And the related function names in my file are "b.va = function(a, c)" and "var ue = function(a, c, d, e, f, g)"