Fix incorrect position calculation in CharsetDecoder.

Data OUTPUT_OFFSET always gives us the number of bytes written
on output, so it's sufficient to increment the position by that number.
In particular, we do not have to subtract arrayOffset() from that
number.

Reported-By: Piotr Jastrzębski <haaawk@google.com>

Change-Id: I39ac470101f72aa4a87e31c4eb0665fe6a162e1d
2 files changed