aura: Remove unused Window::Blur().

aura: Remove unused Window::Blur().

The last use of Window::Blur() was removed recently (crrev.com/329087). So
remove it now.

BUG=none

Committed: https://crrev.com/83376fd7fe58d4cde8563b33a6da259fae85faec
Cr-Commit-Position: refs/heads/master@{#329168}

[sadrul, 2015-05-11 16:12:21]

sadrul@chromium.org changed reviewers:
+ sky@chromium.org

[sky, 2015-05-11 16:49:25]

LGTM

[sadrul, 2015-05-11 17:03:41]

The CQ bit was checked by sadrul@chromium.org

[commit-bot: I haz the power, 2015-05-11 17:09:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1135063002/1

[commit-bot: I haz the power, 2015-05-11 17:33:08]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-11 17:34:23]

Patchset 1 (id:??) landed as
https://crrev.com/83376fd7fe58d4cde8563b33a6da259fae85faec
Cr-Commit-Position: refs/heads/master@{#329168}