Introduce visiblePositionOf() with PositionWithAffinity as replacement of VisiblePosition constructo

Introduce visiblePositionOf() with PositionWithAffinity as replacement of VisiblePosition constructor

This patch introduces |visiblePositionOf()| with |PositionWithAffinity| as
replacement of |VisiblePosition| constructor with |PositionWithAffinity| to
prepare making |VisiblePosition| constructors private.

This patch is a preparation of making selection to handle granularity for web
component, http://crrev.com/1277863002

BUG=513568
TEST=n/a; no behavior changes

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=201518

[yosin_UTC9, 2015-09-01 03:01:33]

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

[yosin_UTC9, 2015-09-01 03:01:56]

PTAL

[tkent, 2015-09-01 04:01:54]

lgtm.

Maybe it's too late, but I feel the function name should start with a verb
because it's not a simple accessor.

[yosin_UTC9, 2015-09-01 04:06:27]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-09-01 04:06:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1326563002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1326563002/1

[commit-bot: I haz the power, 2015-09-01 04:15:40]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201518

[yosin_UTC9, 2015-09-01 04:25:32]

On 2015/09/01 04:01:54, tkent wrote:
> lgtm.
> 
> Maybe it's too late, but I feel the function name should start with a verb
> because it's not a simple accessor.

I'll rename to |computeVisiblePosition()|.