...and ~SystemWindow can recursively destroy its child windows

...so when the pMyParent vs. pMySysWin typos in the asserts (thanks Matteo and
Micheal for spotting) were fixed, they would fire in such scenarios.  So just
hope that it is fine to effectively skip those safety checks in these cases,
too.

Change-Id: Ib925e57b68643c75a5d4db67fd64692015482179
Clean up OutputDevice and derived classes noncopyable-ness

Change-Id: Id29e52c94a89cac20e29ae0a1f0b9f90ffdfcf09