Implement learn more bubble on views.

Screenshots: http://imgur.com/a/3w2eO

Behavior I'd like to add in a separate CL:
- make the bubble show upward if not enough bottom space

BUG=258553
R=estade@chromium.org,thestig@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/55243005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233255 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233255