Templatize handleMousePressEventSingleClick in SelectionController

Templatize handleMousePressEventSingleClick in SelectionController

This patch introduces a template function |handleMousePressEventSingleClickAlgorithm<Strategy>|
for a preparation of making |handleMousePressEventSingleClick()| to work with both
DOM tree and composed tree.

Following patch will make |expandSelectionToRespectUserSelectAll()| to check
runtime flag |SelectionForWebComponents| and work for either positions in DOM
tree or positions in 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=197460

[yosin_UTC9, 2015-06-19 07:42:39]

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

[yosin_UTC9, 2015-06-19 07:42:39]

PTAL

[tkent, 2015-06-19 07:59:46]

The CQ bit was checked by tkent@chromium.org

[tkent, 2015-06-19 07:59:46]

lgtm

[commit-bot: I haz the power, 2015-06-19 07:59:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1191253002/1

[commit-bot: I haz the power, 2015-06-19 08:18:41]

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

[commit-bot: I haz the power, 2015-06-19 08:18:43]

Try jobs failed on following builders:
  mac_blink_rel on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/mac_blink_rel/builds/59732)

[yosin_UTC9, 2015-06-19 08:59:48]

The CQ bit was checked by yosin@chromium.org

[yosin_UTC9, 2015-06-19 08:59:49]

The patchset sent to the CQ was uploaded after l-g-t-m from tkent@chromium.org
Link to the patchset: https://codereview.chromium.org/1191253002/#ps20001
(title: "2015-06-19T17:58:51")

[commit-bot: I haz the power, 2015-06-19 09:00:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1191253002/20001

[commit-bot: I haz the power, 2015-06-19 10:18:07]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197460