shiny/widget: introduce the NodeWrapper type.

This eliminates the ".Node" in a number of "foo.Node" expressions.

Change-Id: I1e6c72a9e3244c7f2731ed4b6180316b53ce43f3
Reviewed-on: https://go-review.googlesource.com/22828
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>
4 files changed