msLaunchUri method in Project Spartan/Edge

Dear Microsoft team,

We are currently evaluating Windows 10 (Build 10130) and especially Project Spartan/Edge regarding its custom URL scheme behaviour. We found a way to check if a protocol handler is exists, fromhttp://msdn.microsoft.com/en-us/library/dn705405(v=vs.85).aspx.  it is navigator.msLaunchUri method.

However, in Project Spartan/Edge, it dosen't work like the MSDN document. successCallback(2nd parameter) and noHandlerCallback(3rd parameter) are never called.

Is it a bug? if it is not a bug(document is wrong), is there another way to check if a protocol handler is exists? That functionality is very important for our product.

Sincerly Yours,