copy method
Creates a copy of this instance.
Implementation
DOMContext<T> copy() {
var context = DOMContext(
parent: parent,
viewport: viewport,
resolveCSSViewportUnit: resolveCSSViewportUnit);
context.domGenerator = domGenerator;
context.namedElementAttribute = namedElementAttribute;
context.namedElementProvider = namedElementProvider;
context.variables = Map.from(deepCopy(variables)!);
context.intlMessageResolver = intlMessageResolver;
return context;
}