Fix two issues with HoverHighlightView

Fix two issues with HoverHighlightView

1) Set the enable status of icon and label before it's being added as a
child of HoverHighlightView

2) Refuse SetHoverHightlight to true when disabled, and SetHoverHightlight
to false when OnEnabledChanged triggered and enabled() changed to false.

BUG=560013, 560027
Committed: https://crrev.com/b1d79c3bae7353740e891513770e8fccdb19b2f4
Cr-Commit-Position: refs/heads/master@{#361146}

[fqj, 2015-11-23 00:13:48]

fqj@chromium.org changed reviewers:
+ stevenjb@chromium.org

[fqj, 2015-11-23 00:13:48]

PTAL.

[stevenjb, 2015-11-23 17:59:27]

lgtm

[fqj, 2015-11-23 18:07:28]

The CQ bit was checked by fqj@chromium.org

[commit-bot: I haz the power, 2015-11-23 18:09:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1470783002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1470783002/1

[commit-bot: I haz the power, 2015-11-23 18:22:16]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-23 18:23:06]

Patchset 1 (id:??) landed as
https://crrev.com/b1d79c3bae7353740e891513770e8fccdb19b2f4
Cr-Commit-Position: refs/heads/master@{#361146}