I wonder if we should use an icon here rather than a string.

Possible examples:
http://www.infragistics.com/community/blogs/damyan_petev/archive/2012/06/08/the-xaml-data-chart-now-with-overview-plus-detail-pane.aspx
(the icon with the four arrows pointing out)

http://www.blazeaudio.com/howto/edit-zooming.html
(icon in the top right with the two arrows)

And then "Reset Zoom" could be the alt text. We could use a data URL to avoid dependencies on external images, just like the range selector does.