Move computeInlineBoxPosition() to VisibleUnits.{cpp,h} from Position.{cpp,h} and VisiblePosition.h

Move computeInlineBoxPosition() to VisibleUnits.{cpp,h} from Position.{cpp,h} and VisiblePosition.h

This patch moves |computeInlineBoxPosition()| to "VisibleUnits.{cpp,h} from
"Position.{cpp,h}" and "VisiblePosition.{cpp,h}" to consolidate |InlineBox|
dependency to "VisibleUnits.cpp" for ease of working them later.

BUG=518738
TEST=n/a; no behavior changes

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200970

[yosin_UTC9, 2015-08-21 05:00:03]

yosin@chromium.org changed reviewers:
+ hajimehoshi@chromium.org, yoichio@chromium.org

[yosin_UTC9, 2015-08-21 05:11:29]

PTAL

[yoichio, 2015-08-21 07:01:10]

lgtm

[yosin_UTC9, 2015-08-21 07:24:19]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-08-21 07:24:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1303173002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1303173002/1

[commit-bot: I haz the power, 2015-08-21 07:29:34]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=200970