The mPos field in the MeasuredText object is relative to the start of
the text (mTextStart), but the pos passed in by the caller of the
setPos() method is relative to the character sequence. When spans
overlap break boundaries and the paragraph doesn't start at 0, the
result is an out of bounds error. This fix uses the correct offset.
Change-Id: I12c7a2311a9bdbbea7ab21554a922b7f665a17bf
1341ab6f38