Up to Chrome V27 you could enumerate Chrome child window controls to get to the edit field and read the string value from there to get the current opened URL.
Unfortunately Chrome 28 has switched to the new rendering Engine (Blink) and does not use Windows controls anymore besides the main window (Chrome_WidgetWin_1) and the web page tab (Chrome_RenderWidgetHostHWND).
I would be grateful if someone could point to an alternative method of getting the currently opened Chrome URL from another (Win32) application.