pkg/csslib: fixed analysis error, more cleanup

pkg/csslib/lib/visitor.dart

Index: pkg/csslib/lib/visitor.dart
diff --git a/pkg/csslib/lib/visitor.dart b/pkg/csslib/lib/visitor.dart
index 3b20a4ec18ef2770d2b9d3aec6aa739b12c93702..6c009ff012344717988f9f8796f2d0682750f2ab 100644
--- a/pkg/csslib/lib/visitor.dart
+++ b/pkg/csslib/lib/visitor.dart
@@ -111,7 +111,7 @@ abstract class VisitorBase {
 /** Base vistor class for the style sheet AST. */
 class Visitor implements VisitorBase {
   /** Helper function to walk a list of nodes. */
-  void _visitNodeList(list) {
+  void _visitNodeList(List<TreeNode> list) {
     // Don't use iterable otherwise the list can't grow while using Visitor.
     // It certainly can't have items deleted before the index being iterated
     // but items could be added after the index.
@@ -194,7 +194,7 @@ class Visitor implements VisitorBase {
   }
 
   void visitStyletDirective(StyletDirective node) {
-    _visitNodeList(node._rulesets);
+    _visitNodeList(node.rulesets);
   }
 
   void visitNamespaceDirective(NamespaceDirective node) { }
@@ -230,7 +230,7 @@ class Visitor implements VisitorBase {
   }
 
   void visitDeclarationGroup(DeclarationGroup node) {
-    _visitNodeList(node._declarations);
+    _visitNodeList(node.declarations);
   }
 
   void visitMarginGroup(MarginGroup node) => visitDeclarationGroup(node);
@@ -329,7 +329,7 @@ class Visitor implements VisitorBase {
       visitSimpleSelector(node);
 
   void visitSelectorExpression(SelectorExpression node) {
-    _visitNodeList(node._expressions);
+    _visitNodeList(node.expressions);
   }
 
   void visitUnicodeRangeTerm(UnicodeRangeTerm node) { }