Introduce localCaretRectOf() for VisiblePosition

Introduce localCaretRectOf() for VisiblePosition

This patch introduces |localCaretRectOf()| function for |VisiblePosition| as
replacement of |VisiblePosition::localCaretRect()| to simplify |VisiblePosition|
class for ease of templataizing |VisiblePosition| class to introduce composed
tree version of |VisiblePosition|, since an implementation of
|VisiblePosition::localCaretRect()| can be implemented with public member
functions of |VisiblePosition| class.

This patch is a preparation of making selection to handle granularity for web
component, http://crrev.com/1277863002

BUG=513568
TEST=n/a; No behavior changes

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=201409

[yosin_UTC9, 2015-08-28 09:40:10]

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

[yosin_UTC9, 2015-08-28 09:40:11]

PTAL

[hajimehoshi, 2015-08-28 09:42:19]

lgtm

[yosin_UTC9, 2015-08-28 10:01:48]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-08-28 10:01:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1325443002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1325443002/1

[commit-bot: I haz the power, 2015-08-28 10:06:47]

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

[commit-bot: I haz the power, 2015-08-28 10:06:48]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[yosin_UTC9, 2015-08-28 14:09:07]

The CQ bit was checked by yosin@chromium.org

[yosin_UTC9, 2015-08-28 14:09:08]

The patchset sent to the CQ was uploaded after l-g-t-m from
hajimehoshi@chromium.org
Link to the patchset: https://codereview.chromium.org/1325443002/#ps20001
(title: "2015-08-28T23:08:19 Rebase after absoluteCaretRectBoundsOf()")

[commit-bot: I haz the power, 2015-08-28 14:09:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1325443002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1325443002/20001

[commit-bot: I haz the power, 2015-08-28 16:15:46]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201409