Templatize PendingSelection class

Templatize PendingSelection class

Now |PendingSelection| works only on DOM tree. This patch templatizes
|PendingSelection| class and end enables it to allow other node-traversing
strategies, such as composed tree.

This patch is result of collaboration work with hajimehoshi@chromium.org
for selection of web components. After this patch, we are going to
implement another strategies for the composed tree. We've already
prepared that at http://crrev.com/1106433002.

BUG=275851
TEST=n/a; No behavior changes.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197256

[yosin_UTC9, 2015-06-17 08:02:06]

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

[yosin_UTC9, 2015-06-17 08:02:09]

PTAL

[tkent, 2015-06-17 08:14:29]

lgtm

https://codereview.chromium.org/1189963003/diff/1/Source/core/editing/Visible...
File Source/core/editing/VisibleSelection.h (right):

https://codereview.chromium.org/1189963003/diff/1/Source/core/editing/Visible...
Source/core/editing/VisibleSelection.h:46: class InDOMTree {
The name |InDOMTree| sounds weird though I have no alternative idea.

[yosin_UTC9, 2015-06-17 08:58:23]

On 2015/06/17 08:14:29, tkent wrote:
> lgtm
> 
>
https://codereview.chromium.org/1189963003/diff/1/Source/core/editing/Visible...
> File Source/core/editing/VisibleSelection.h (right):
> 
>
https://codereview.chromium.org/1189963003/diff/1/Source/core/editing/Visible...
> Source/core/editing/VisibleSelection.h:46: class InDOMTree {
> The name |InDOMTree| sounds weird though I have no alternative idea.

Once, we have an option for name, we'll rename.

[yosin_UTC9, 2015-06-17 08:58:28]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-06-17 08:58:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1189963003/1

[commit-bot: I haz the power, 2015-06-17 11:05:57]

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

[commit-bot: I haz the power, 2015-06-17 11:05:58]

Try jobs failed on following builders:
  win_blink_rel on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/66984)

[hajimehoshi, 2015-06-17 11:13:51]

The CQ bit was checked by hajimehoshi@chromium.org

[commit-bot: I haz the power, 2015-06-17 11:14:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1189963003/1

[commit-bot: I haz the power, 2015-06-17 12:16:49]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197256