Use tighter typing in editing: SimplifyMarkupCommand & TextIterator

Use tighter typing in editing: SimplifyMarkupCommand & TextIterator

Use tighter typing in editing to increase code readability. This CL focuses
on SimplifyMarkupCommand and TextIterator.

R=yosin@chromium.org, leviw@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=179525

[leviw_travelin_and_unemployed, 2014-08-04 18:53:47]

Nice. LGTM.

[commit-bot: I haz the power, 2014-08-04 18:54:19]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/443433003/1

[commit-bot: I haz the power, 2014-08-04 19:37:22]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/20591)

[commit-bot: I haz the power, 2014-08-04 19:51:00]

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

[commit-bot: I haz the power, 2014-08-04 19:51:01]

Try jobs failed on following builders:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/20604)

[Inactive, 2014-08-04 19:58:49]

The CQ bit was checked by ch.dumez@samsung.com

[commit-bot: I haz the power, 2014-08-04 19:59:43]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/443433003/1

[commit-bot: I haz the power, 2014-08-04 20:42:07]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/20611)

[commit-bot: I haz the power, 2014-08-04 21:21:15]

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

[commit-bot: I haz the power, 2014-08-04 21:21:16]

Try jobs failed on following builders:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/20625)

[Inactive, 2014-08-04 23:30:45]

The CQ bit was checked by ch.dumez@samsung.com

[commit-bot: I haz the power, 2014-08-04 23:31:46]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/443433003/1

[commit-bot: I haz the power, 2014-08-05 00:11:47]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/20672)

[commit-bot: I haz the power, 2014-08-05 01:12:17]

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

[commit-bot: I haz the power, 2014-08-05 01:12:18]

Try jobs failed on following builders:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/20683)

[Inactive, 2014-08-05 13:06:01]

The CQ bit was checked by ch.dumez@samsung.com

[commit-bot: I haz the power, 2014-08-05 13:09:03]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/443433003/1

[commit-bot: I haz the power, 2014-08-05 14:37:36]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/20927)

[commit-bot: I haz the power, 2014-08-05 16:06:58]

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

[commit-bot: I haz the power, 2014-08-05 16:06:59]

Try jobs failed on following builders:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/20966)

[Inactive, 2014-08-05 19:07:43]

The CQ bit was checked by ch.dumez@samsung.com

[commit-bot: I haz the power, 2014-08-05 19:09:18]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/443433003/1

[commit-bot: I haz the power, 2014-08-05 21:07:33]

Change committed as 179525