In Chrome-like browsers, TextInputWidget( { type: 'search' } ) has a curious mix of native and our UI.
http://en.wikipedia.beta.wmflabs.org/wiki/Special:Search:
http://en.wikipedia.beta.wmflabs.org/wiki/Special:Search?useskin=monobook:
The "x" image on the right is provided by the browser, and empties the text field when clicked (but isn't focusable). We should probably suppress it and replace it with an indicator of our own with the same functionality.
(This widget also has icon: 'search', which should maybe also be implied by type: 'search'?)