Add a better getLastQueuedBuffer

Avoid obfuscation via a matrix that's not necessarily useful or in
the desired origin of the caller. Instead return the source data,
which is also a lot smaller than the matrix is...

Bug: 183553027
Test: atest android.view.cts.PixelCopyTest (+new testBufferQueueCrop)
Change-Id: I1f7b5981405b2f20293bce9119414fc7780b8eb6
Merged-In: I1f7b5981405b2f20293bce9119414fc7780b8eb6