Make IconLabelBubbleView a views::LabelButton

IconLabelBubbleView was already semantically a LabelButton: it had an
image, a label, and an InkDropContainerView. This makes it derive from
LabelButton instead of Button and removes some duplicated code.

Follow up changes will remove more duplicated code.

Change-Id: Ief4f0dfa24794b953ff54af9d34422edbeaaf733
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1525443
Reviewed-by: Dana Fried <dfried@chromium.org>
Commit-Queue: Collin Baker <collinbaker@chromium.org>
Cr-Commit-Position: refs/heads/master@{#643640}
12 files changed