Register a key callback to handle back key event with untrusted certificate confirm...

Register a key callback to handle back key event with untrusted certificate confirm popup

    - This applies to the permission request popup for untrusted certificate confirm

[Issue#]   N/A
[Problem]  A web page underneath pop-up moves to the previous page when user expects the pop-up closed.
[Cause]    The permission request pop-up did not handle the back-key callback.
[Solution] Register the key callback.

[SCMRequest] N/A

Change-Id: Iddee71ee6414a24326eeedd083601571e5726cc7