GitLab

Currently, the extensions can go in an incorrect
hover state when they're being reordered via drag
and drop. This bug fixes it by preventing the buttons
to enter the hover state when a button is dragged.

Bug: 793572
Change-Id: I1275882b68bbafd901f5edeab4e5c9b93286e699
Reviewed-on: https://chromium-review.googlesource.com/874523Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Sarah Chan <spqchan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532948}