Move inRenderedText() to VisibleUnits.cpp from Position.cpp

Move inRenderedText() to VisibleUnits.cpp from Position.cpp

This patch moves |inRenderedText()| to "VisibleUnits.cpp" from "Position.cpp"
to simplify "Position.cpp" for improving code health since it is used only in
"VisibleUnits.cpp"

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

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200981

[yosin_UTC9, 2015-08-21 08:56:21]

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

[yosin_UTC9, 2015-08-21 09:30:08]

PTAL

[yosin_UTC9, 2015-08-21 11:15:10]

yosin@chromium.org changed reviewers:
+ keishi@chromium.org

[hajimehoshi, 2015-08-21 11:46:10]

lgtm

[hajimehoshi, 2015-08-21 11:46:13]

The CQ bit was checked by hajimehoshi@chromium.org

[commit-bot: I haz the power, 2015-08-21 11:46:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1309673002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1309673002/1

[commit-bot: I haz the power, 2015-08-21 11:50:39]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=200981