Really make Surface thread-safe.

There were many places where the native object was being
accessed improperly.  Also some places where CloseGuard might
not be acquired or released correctly or where the generation
count might not be updated.

Fixed them all.

That said, Surface isn't intended to be used concurrently
so please don't do it.  This is only intended to make
hard to find crashes less likely.

Bug: 8328715
Change-Id: I981ef33425823e0fd7ad6b64443f2ec9b0c8335e