Replace forward class declarations of VisibleSelection to include directive

Replace forward class declarations of VisibleSelection to include directive

This patch replaces forward class declarations |VisibleSelection| to include
directive of "VisibleSelection.h" as preparation of introducing
|VisibleSelectionTemplate<Strategy>|, like |PositionAlgorithm<Strategy>|.

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=201215

[yosin_UTC9, 2015-08-26 06:08:59]

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

[yosin_UTC9, 2015-08-26 06:09:09]

PTAL

[yoichio, 2015-08-26 06:12:39]

lgtm

[yosin_UTC9, 2015-08-26 06:13:32]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-08-26 06:13:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1314843003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1314843003/1

[commit-bot: I haz the power, 2015-08-26 07:46:25]

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

[commit-bot: I haz the power, 2015-08-26 07:46:25]

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

[yosin_UTC9, 2015-08-26 07:51:20]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-08-26 07:51:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1314843003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1314843003/1

[commit-bot: I haz the power, 2015-08-26 08:29:01]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201215