Use tighter typing in editing: DeleteSelectionCommand

Use tighter typing in editing: DeleteSelectionCommand

Use tighter typing in editing to increase code readability.
This CL focuses on DeleteSelectionCommand.

R=leviw@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=179072

[yosin_UTC9, 2014-07-28 01:01:22]

LGTM

It is more readabile. Thanks!
Please wait for OWNERS lgtm for committing.

[leviw_travelin_and_unemployed, 2014-07-28 21:36:16]

owners lgtm

[commit-bot: I haz the power, 2014-07-28 21:37:17]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/420053002/1

[commit-bot: I haz the power, 2014-07-28 21:41:06]

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

[commit-bot: I haz the power, 2014-07-28 21:43:32]

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

[commit-bot: I haz the power, 2014-07-28 21:43:32]

Try jobs failed on following builders:
  blink_presubmit on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/blink_presubmit/builds/1...)

[Inactive, 2014-07-28 22:25:59]

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

[commit-bot: I haz the power, 2014-07-28 22:26:28]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/420053002/20001

[commit-bot: I haz the power, 2014-07-29 00:05:20]

Change committed as 179072