tree 89f683aa3322a9c5fdf0084e881e27dcb1379126
parent 959aaed3b215c739952ce4abf536d7bf4b84634d
author Sigmund Cherem <sigmund@google.com> 1463008074 -0700
committer Sigmund Cherem <sigmund@google.com> 1463008074 -0700

Make TreeNode.visit return dynamic.

Subclasses of TreeNode already do `visit(visitor) =>
visitor.visitSomething(this)`, this just exposes it at the root of the tree
hierarchy.  This is needed for package:html, where we have code that would do
the equivalent of `x = node.visit(myVisitor)`.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//1969953002 .