public class DockLayoutPanelParser
Parses DockLayoutPanel widgets.
TODO(jgw): The code that explicitly excludes SplitLayoutPanel in a fairly
awkward way could be greatly simplified if we hoisted the "dock-ness" into an
interface implemented by both DockLayoutPanel and SplitLayoutPanel, and moved
most of this code into a parser for that specific interface. This parser
would then be reduced to a simple special case for the ctor param.