A variety of cleanups to bring our samples up-to-date.

utils/css/tree.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Generated by scripts/tree_gen.py.
 
 /////////////////////////////////////////////////////////////////////////
 // CSS specific types:
 /////////////////////////////////////////////////////////////////////////
 
 
@@ skipping 108 matching lines @@
       _combinator == TokenKind.COMBINATOR_DESCENDANT;
 
   String _combinatorToString() =>
       isCombinatorDescendant() ? ' ' :
       isCombinatorPlus() ? '+' :
       isCombinatorGreater() ? '>' :
       isCombinatorTilde() ? '~' : '';
 
   visit(TreeVisitor visitor) => visitor.visitSimpleSelectorSequence(this);
 
-  String toString() => _combinatorToString() + _selector.toString();
+  String toString() => "${_combinatorToString()}${_selector.toString()}";
 }
 
 /* All other selectors (element, #id, .class, attribute, pseudo, negation,
  * namespace, *) are derived from this selector.
  */
 class SimpleSelector extends ASTNode {
   var _name;
 
   SimpleSelector(this._name, SourceSpan span) : super(span);
 
@@ skipping 189 matching lines @@
 
   RuleSet(this._selectorGroup, this._declarationGroup, SourceSpan span) :
       super(span);
 
   SelectorGroup get selectorGroup => _selectorGroup;
   DeclarationGroup get declarationGroup => _declarationGroup;
 
   visit(TreeVisitor visitor) => visitor.visitRuleSet(this);
 
   String toString() =>
-      "\n${_selectorGroup.toString()} {\n" +
+      "\n${_selectorGroup.toString()} {\n"
         "${_declarationGroup.toString()}}\n";
 }
 
 class Directive extends ASTNode {
   Directive(SourceSpan span) : super(span);
 
   String toString() => "Directive";
 
   bool get isBuiltIn => true;       // Known CSS directive?
   bool get isExtension => false;    // SCSS extension?
@@ skipping 908 matching lines @@
     output.heading('BinaryExpression', node.span);
     // TODO(terry): TBD
   }
 
   void visitUnaryExpression(UnaryExpression node) {
     output.heading('UnaryExpression', node.span);
     // TODO(terry): TBD
   }
 
   void visitIdentifier(Identifier node) {
-    output.heading('Identifier(' + output.toValue(node.name) + ")", node.span);
+    output.heading('Identifier(${output.toValue(node.name)})', node.span);
   }
 
   void visitWildcard(Wildcard node) {
     output.heading('Wildcard(*)', node.span);
   }
 
   // TODO(terry): Defined for frog/tree.dart.
   void visitTypeReference(TypeReference node) {
     output.heading('Unimplemented');
   }
 }