Improve canBeAnchorNode() for PositionInFlatTree constructor

Improve canBeAnchorNode() for PositionInFlatTree constructor

This patch changes |canBeAnchorNode()| for |PositionInFlatTree| constructor
to check whether specified node can be participate to flat tree or not to
improve debug experience.

This patch is a preparation of http://crrev.com/2221783003, which attempt to
call |toPositionInFlatTree()| with a position which uses |ShadowRoot| as
anchor node.

BUG=139552, 632333
TEST=n/a; no behavior changes

Committed: https://crrev.com/d0bf55edc59dd1399c5892f1afb2643ea978bddb
Cr-Commit-Position: refs/heads/master@{#410629}

[yosin_UTC9, 2016-08-09 04:48:59]

Description was changed from

==========
2016-08-09T13:48:05

BUG=
==========

to

==========
Improve canBeAnchorNode() for PositionInFlatTree constructor

This patch changes |canBeAnchorNode()| for |PositionInFlatTree| constructor
to check whether specified node can be participate to flat tree or not to
improve debug experience.

This patch is a preparation of http://crrev.com/2221783003, which attempt to
call |toPositionInFlatTree()| with a position which uses |ShadowRoot| as
anchor node.

BUG=139552, 632333
TEST=n/a; no behavior changes
==========

[yosin_UTC9, 2016-08-09 04:49:04]

The CQ bit was checked by yosin@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-09 04:54:30]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-09 06:58:53]

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

[commit-bot: I haz the power, 2016-08-09 06:58:54]

Dry run: Try jobs failed on following builders:
  win_chromium_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[yosin_UTC9, 2016-08-09 07:19:42]

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

[yosin_UTC9, 2016-08-09 07:19:43]

PTAL

[Xiaocheng, 2016-08-09 09:12:14]

lgtm

[yosin_UTC9, 2016-08-09 09:31:25]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2016-08-09 09:31:58]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-09 10:54:28]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-09 10:55:48]

Description was changed from

==========
Improve canBeAnchorNode() for PositionInFlatTree constructor

This patch changes |canBeAnchorNode()| for |PositionInFlatTree| constructor
to check whether specified node can be participate to flat tree or not to
improve debug experience.

This patch is a preparation of http://crrev.com/2221783003, which attempt to
call |toPositionInFlatTree()| with a position which uses |ShadowRoot| as
anchor node.

BUG=139552, 632333
TEST=n/a; no behavior changes
==========

to

==========
Improve canBeAnchorNode() for PositionInFlatTree constructor

This patch changes |canBeAnchorNode()| for |PositionInFlatTree| constructor
to check whether specified node can be participate to flat tree or not to
improve debug experience.

This patch is a preparation of http://crrev.com/2221783003, which attempt to
call |toPositionInFlatTree()| with a position which uses |ShadowRoot| as
anchor node.

BUG=139552, 632333
TEST=n/a; no behavior changes

Committed: https://crrev.com/d0bf55edc59dd1399c5892f1afb2643ea978bddb
Cr-Commit-Position: refs/heads/master@{#410629}
==========

[commit-bot: I haz the power, 2016-08-09 10:55:49]

Patchset 1 (id:??) landed as
https://crrev.com/d0bf55edc59dd1399c5892f1afb2643ea978bddb
Cr-Commit-Position: refs/heads/master@{#410629}