View network activity for browser child window

View network activity for browser child window

I need to reverse-engineer some javascript application which does
authorization using facebook auth.
Facebook auth window pops up, asks for my permissions, and gets closed
instantly, so I am unable to grasp anything from the performed action, as
it's too fast.
The problem is that neither Chrome DevTools, nor Firefox Firebug does
display network activity for child windows like OAuth permission.
Is there a way to enable FULL network log? An extension, whatever? (It
better be free and easy to use)