We need to update mPos when we copy a FieldPacker via its data[] member.

Bug: 15756600

This change also adds a TODO/FIXME related to subAlign() and our tracking
mechanism for it. We need to further investigate how to make subAlign() work
properly if a user copies their FieldPacker.

Change-Id: I861e529abd11e378f7c73b510d7f418b940fe480
1 file changed