Update composed tree version of isEndOfEditableOrNonEditableContent()

Update composed tree version of isEndOfEditableOrNonEditableContent() to handle a positions in INPUT/TEXTAREA element

This patch makes composed tree version of
|isEndOfEditableOrNonEditableContent()| to handle a position in INPUT/TEXTAREA
element as same as DOM tree version as a preparation of introducing full version
of |VisibleSelectionTemplate|.

Before this patch, composed tree version of
|isEndOfEditableOrNonEditableContent()| returns false for the last position of
inner editor in INPUT/TEXTAREA element, but DOM version of it returns true.
Because of the last position of inner editor is the last position of
shadow DOM tree and there are no next position. However, in composed tree,
next position of the last position of inner editor is a position after
INPUT/TEXTAREA element.

This patch is a preparation of making selection to handle granularity for web
component, http://crrev.com/1363873004

BUG=513568
TEST=VisibleUnitsTest.isEndOfEditableOrNonEditableContentWithInput

Committed: https://crrev.com/311966e56451f2b03668a4866fb7a886a0e05ad9
Cr-Commit-Position: refs/heads/master@{#350803}

[yosin_UTC9, 2015-09-25 07:19:13]

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

[yosin_UTC9, 2015-09-25 07:21:24]

PTAL

[tkent, 2015-09-25 09:18:29]

The CQ bit was checked by tkent@chromium.org

[tkent, 2015-09-25 09:18:29]

lgtm

[commit-bot: I haz the power, 2015-09-25 09:18:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1365263002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1365263002/1

[commit-bot: I haz the power, 2015-09-25 11:21:48]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-25 11:23:10]

Patchset 1 (id:??) landed as
https://crrev.com/311966e56451f2b03668a4866fb7a886a0e05ad9
Cr-Commit-Position: refs/heads/master@{#350803}