Moves an implementation of LayoutView::commitPendingSelection() to PendingSelection::commit()

Moves an implementation of LayoutView::commitPendingSelection() to PendingSelection::commit()

This patch moves an implementation of |LayoutView::commitPendingSelection()| to
|PendingSelection::commit()| as a preparation of moving it to "editing/",
for reducing exposing editing functions to layout layer.

Following patch will move |PendingSelection| to "editing/".

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=201854

[yosin_UTC9, 2015-09-07 03:25:37]

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

[yosin_UTC9, 2015-09-07 03:25:45]

PTAL

[tkent, 2015-09-07 03:57:46]

lgtm

[yosin_UTC9, 2015-09-07 04:15:26]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-09-07 04:15:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1315423006/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1315423006/1

[commit-bot: I haz the power, 2015-09-07 04:19:40]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201854