[Media Router WebUI] Fix search focus handlers when search is enabled

[Media Router WebUI] Fix search focus handlers when search is enabled

This change corrects the point of setting the search focus handlers to
be after search first becomes enabled. Previously it was set in ready(),
but since disabling search by default, the handlers weren't correctly
updated.

BUG=592723
R=apacible@chromium.org
NOTRY=true
NOPRESUBMIT=true

Review-Url: https://codereview.chromium.org/2012593002
Cr-Commit-Position: refs/heads/master@{#395774}
(cherry picked from commit e5e7577ef96ee5fa24c8952e649312dc5427aa42)

[btolsch, 2016-06-01 21:28:09]

Merge to M52, no conflicts. PTAL, thanks!

[apacible, 2016-06-01 22:30:17]

lgtm

[btolsch, 2016-06-01 22:37:59]

The CQ bit was checked by btolsch@chromium.org

[commit-bot: I haz the power, 2016-06-01 22:39:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2033473002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/2033473002/1

[commit-bot: I haz the power, 2016-06-01 22:40:35]

Committed patchset #1 (id:1)