Use Position and PositionInComposedTree to create VisiblePosition at SelectionController

Use Position and PositionInComposedTree to create VisiblePosition at SelectionController

At SelectionController, VisiblePositions are now created only with
Position. To make VisiblePosition work on the composed tree
correctly, we need to pass different types of positions to
VisiblePositions. This CL changes the types of positions to pass
by using Strategy::toPositionType.

This CL is a preparation. Now both constructors that take Position
and PositionInComposedTree are functionally same, but we are going to
fix this (crrev.com/1106433002).

This patch is result of collaboration work with yosin@chromium.org
for selection of web components. We are now preparing this feature at
crrev.com/1106433002.

BUG=275851
TEST=n/a; no behavior change

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197631

[hajimehoshi, 2015-06-23 05:31:46]

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

[hajimehoshi, 2015-06-23 05:31:47]

PTAL

[yosin_UTC9, 2015-06-23 05:33:21]

Since, I'm co-author of this patch. I'm not a good person for review.

[tkent, 2015-06-23 05:50:10]

> As a preparation for selection on the composed tree, VisiblePosition
> should be created with not only Position/PositionInComposedTree but also
> their affinities. This is necessary for VisiblePosition to work on the
> composed tree correctly.

Is this a correct explanation of the change?
VisiblePosition(const PositionWithAffinity&) used in the old code respects the
affinity field of the specified PositionWithAffinity.

[hajimehoshi, 2015-06-23 06:09:59]

On 2015/06/23 05:50:10, tkent wrote:
> > As a preparation for selection on the composed tree, VisiblePosition
> > should be created with not only Position/PositionInComposedTree but also
> > their affinities. This is necessary for VisiblePosition to work on the
> > composed tree correctly.
> 
> Is this a correct explanation of the change?
> VisiblePosition(const PositionWithAffinity&) used in the old code respects the
> affinity field of the specified PositionWithAffinity.

Updated the description. Sorry but the explanation was wrong.

The key is that we need to pass Position and/or PositionInComposedTree to
the constructor of VisiblePosition.

PTAL

[tkent, 2015-06-23 06:12:34]

The CQ bit was checked by tkent@chromium.org

[tkent, 2015-06-23 06:12:34]

lgtm

[commit-bot: I haz the power, 2015-06-23 06:12:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1205563002/1

[commit-bot: I haz the power, 2015-06-23 07:21:09]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197631