textblock: Update visual_pos before calling _size_native_calc_line_finalize.

textblock: Update visual_pos before calling _size_native_calc_line_finalize.

Summary:
In items loop of _size_native_calc_line_finalize,
last_it should be replaced with new item according to position.
But, visual_pos is not prepared and it is always zero in the function.
So, we need to update visual_pos.
And when textblock only has LTR text,
we can replace last_it according to item list sequence.
@fix

Test Plan:
It includes test cases using the following test case.
 1. "i<b>。</b>"
 2. "。<b>i</b>"

Reviewers: seoz, woohyun, sohyun, tasn

Subscribers: raster, herdsman, cedric

Differential Revision: https://phab.enlightenment.org/D859