GitLab

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

Review URL: https://codereview.chromium.org/1470783002

Cr-Commit-Position: refs/heads/master@{#361146}