Revert "New hook, MobileSkinCreated"

There's no foolproof in RequestContext against skin creation in non-UI requests, thus we should avoid messing with OutputPage.

This reverts commit e8dfbba2d3be2353bd9b2f17702e8f7e6c9cabcf

Change-Id: I88ab521260d06ea17265b4a8195ae5e2cd01e9df
Merge "Revert "New hook, MobileSkinCreated""