Stagefright: authenticate ANativeWindow.

This change adds a check to verify that the ANativeWindow to which
decoded video buffers are queued sends those buffers to SurfaceFlinger.
The check is done when the buffer content is flagged as protected.  This
change also adds an error in the case where protected buffers are
needed, but an ANativeWindow is not being used as the video destination.

Change-Id: I107c9082d65ef0de4a13594e9535a2053ad5161b
Bug: 4269240