Avoid to use static member function VisibleSelection::selectionType() in PendingSelection class

Avoid to use static member function VisibleSelection::selectionType() in PendingSelection class

This patch replaces static member function |VisibleSelection::selectionType()|
by |VisibleSelection::Strategy::selectionType()| in |PendingSelection| class
as preparation of moving |VisibleSelection::selctionType()| out from
|VisibleSelection| as local static function, since it is used only
|PendingSelection| and |VisibleSelection| classes for ease of templatizing
|VisibleSelection| to introduce composed tree version.

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=201625

[yosin_UTC9, 2015-09-02 04:40:14]

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

[yosin_UTC9, 2015-09-02 04:40:23]

PTAL

[tkent, 2015-09-02 04:52:44]

lgtm

[yosin_UTC9, 2015-09-02 04:57:12]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-09-02 04:57:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1323933003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1323933003/1

[commit-bot: I haz the power, 2015-09-02 06:19:16]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-09-02 06:19:17]

Try jobs failed on following builders:
  linux_chromium_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[yosin_UTC9, 2015-09-02 06:38:14]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-09-02 06:38:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1323933003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1323933003/1

[commit-bot: I haz the power, 2015-09-02 07:32:13]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201625