Introduce Position constructor with const Node&

Introduce Position constructor taking const Node&

This patch introduces |Position| constructor taking |const Node&| to avoid
to use |const_cast<Node*>()| for improving code health.

This patch also changes |Position| constructor taking |Node*| to |const Node*|
to avoid |const_cast| in |const Node&| |Position| constructor.

BUG=734849
TEST=n/a; no behavior changes

Review-Url: https://codereview.chromium.org/2949763002
Cr-Commit-Position: refs/heads/master@{#481128}
Committed: https://chromium.googlesource.com/chromium/src/+/638c26b1f1ba5238cbf4d72075477ab38b15376f

[yosin_UTC9, 2017-06-20 04:45:19]

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

[commit-bot: I haz the power, 2017-06-20 04:45:28]

Dry run: CQ is trying da patch.

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

[yosin_UTC9, 2017-06-20 06:52:59]

Description was changed from

==========
2017-06-20T13:43:23

BUG=734849

2017-06-20T13:43:18
==========

to

==========
Introduce Position constructor taking const Node&

This patch introduces |Position| constructor taking |const Node&| to avoid
to use |const_cast<Node*>()| for improving code health.

This patch also changes |Position| constructor taking |Node*| to |const Node*|
to avoid |const_cast| in |const Node&| |Position| constructor.

BUG=734849
TEST=n/a; no behavior changes
==========

[yosin_UTC9, 2017-06-20 06:53:15]

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

[yosin_UTC9, 2017-06-20 06:53:16]

PTAL

[commit-bot: I haz the power, 2017-06-20 08:55:07]

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

[commit-bot: I haz the power, 2017-06-20 08:55:08]

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_...)

[Xiaocheng, 2017-06-20 17:58:10]

https://codereview.chromium.org/2949763002/diff/1/third_party/WebKit/Source/c...
File third_party/WebKit/Source/core/editing/Position.cpp (right):

https://codereview.chromium.org/2949763002/diff/1/third_party/WebKit/Source/c...
third_party/WebKit/Source/core/editing/Position.cpp:118: :
anchor_node_(const_cast<Node*>(anchor_node)),
I'm not a fan of this... It makes code less intuitive that, after constructing a
Position with a |const Node*|, you can still modify the node with the Position.

In some sense, a Position is kind of like a pointer. So maybe we should have
Position and ConstPosition?

[yosin_UTC9, 2017-06-21 04:26:25]

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

[commit-bot: I haz the power, 2017-06-21 04:26:41]

Dry run: CQ is trying da patch.

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

[yosin_UTC9, 2017-06-21 04:27:02]

PTAL

Add TODO about [1].

[1] 735327 ⚐	Position should hold const Node instead of Node

https://codereview.chromium.org/2949763002/diff/1/third_party/WebKit/Source/c...
File third_party/WebKit/Source/core/editing/Position.cpp (right):

https://codereview.chromium.org/2949763002/diff/1/third_party/WebKit/Source/c...
third_party/WebKit/Source/core/editing/Position.cpp:118: :
anchor_node_(const_cast<Node*>(anchor_node)),
Discuss offline.
We agree on |Position| is constant, we should not change tree structure around
|anchor_node_|.
Thus, |anchor_node_| should be |Member<const Node>| and member functions in
|Position| should
return |const Node*|.

I file the issue[1] for tracking. 
In this patch, I will add TODO for it.

[1] http://crbug.com/735327 ⚐	Position should hold const Node instead of Node

[Xiaocheng, 2017-06-21 04:39:40]

lgtm

[yosin_UTC9, 2017-06-21 04:53:25]

The CQ bit was unchecked by yosin@chromium.org

[yosin_UTC9, 2017-06-21 04:53:28]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2017-06-21 04:53:38]

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, 2017-06-21 06:45:23]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1498020808030090,
"parent_rev": "95f41c431169a0dc380402e6cccb5a48e3fb486a", "commit_rev":
"638c26b1f1ba5238cbf4d72075477ab38b15376f"}

[commit-bot: I haz the power, 2017-06-21 06:45:37]

Description was changed from

==========
Introduce Position constructor taking const Node&

This patch introduces |Position| constructor taking |const Node&| to avoid
to use |const_cast<Node*>()| for improving code health.

This patch also changes |Position| constructor taking |Node*| to |const Node*|
to avoid |const_cast| in |const Node&| |Position| constructor.

BUG=734849
TEST=n/a; no behavior changes
==========

to

==========
Introduce Position constructor taking const Node&

This patch introduces |Position| constructor taking |const Node&| to avoid
to use |const_cast<Node*>()| for improving code health.

This patch also changes |Position| constructor taking |Node*| to |const Node*|
to avoid |const_cast| in |const Node&| |Position| constructor.

BUG=734849
TEST=n/a; no behavior changes

Review-Url: https://codereview.chromium.org/2949763002
Cr-Commit-Position: refs/heads/master@{#481128}
Committed:
https://chromium.googlesource.com/chromium/src/+/638c26b1f1ba5238cbf4d7207547...
==========

[commit-bot: I haz the power, 2017-06-21 06:45:38]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/chromium/src/+/638c26b1f1ba5238cbf4d7207547...