Introduce composed tree version of rightPositionOf()

Introduce composed tree version of rightPositionOf()

This patch introduces composed tree version of |rightPositionOf()|
by templatizing original |rightPositionOf()| to work both DOM tree
position and composed tree position version for introducing composed tree
version of |VisibleSelection| class.

This patch also templaizes |rightVisuallyDistinctCandidate()| used by
|rightPositionOf()|.

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=201967

[yosin_UTC9, 2015-09-09 07:19:59]

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

[yosin_UTC9, 2015-09-09 07:21:17]

PTAL

It seems ios_rel_device_ninja and ios_dbg_simulator_ninja
are broken. They don't have the latest VisibleUnits.cpp.

[hajimehoshi, 2015-09-09 07:27:27]

lgtm

[yosin_UTC9, 2015-09-09 07:30:41]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-09-09 07:31:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1311803004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1311803004/1

[commit-bot: I haz the power, 2015-09-09 07:32:59]

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

[commit-bot: I haz the power, 2015-09-09 07:33:00]

Try jobs failed on following builders:
  ios_dbg_simulator_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_dbg_simulator...)
  ios_rel_device_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_rel_device_ni...)

[yosin_UTC9, 2015-09-09 08:19:34]

The CQ bit was checked by yosin@chromium.org

[yosin_UTC9, 2015-09-09 08:19:34]

The patchset sent to the CQ was uploaded after l-g-t-m from
hajimehoshi@chromium.org
Link to the patchset: https://codereview.chromium.org/1311803004/#ps20001
(title: "2015-09-09T17:18:38 Rebase")

[commit-bot: I haz the power, 2015-09-09 08:19:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1311803004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1311803004/20001

[commit-bot: I haz the power, 2015-09-09 08:22:16]

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

[commit-bot: I haz the power, 2015-09-09 08:22:17]

Try jobs failed on following builders:
  ios_dbg_simulator_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_dbg_simulator...)
  ios_rel_device_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_rel_device_ni...)

[yosin_UTC9, 2015-09-09 08:56:37]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-09-09 08:56:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1311803004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1311803004/20001

[commit-bot: I haz the power, 2015-09-09 08:59:15]

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

[commit-bot: I haz the power, 2015-09-09 08:59:15]

Try jobs failed on following builders:
  ios_dbg_simulator_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_dbg_simulator...)

[yosin_UTC9, 2015-09-09 09:24:12]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-09-09 09:24:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1311803004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1311803004/20001

[commit-bot: I haz the power, 2015-09-09 09:26:34]

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

[commit-bot: I haz the power, 2015-09-09 09:26:34]

Try jobs failed on following builders:
  ios_rel_device_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_rel_device_ni...)

[yosin_UTC9, 2015-09-09 10:37:22]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-09-09 10:37:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1311803004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1311803004/20001

[commit-bot: I haz the power, 2015-09-09 10:42:00]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201967