Removed obsolete code

utils/css/tree.dart

Index: utils/css/tree.dart
diff --git a/utils/css/tree.dart b/utils/css/tree.dart
deleted file mode 100644
index 08160e452945a18d07f897879febb5a3f3eb2ea8..0000000000000000000000000000000000000000
--- a/utils/css/tree.dart
+++ /dev/null
@@ -1,1279 +0,0 @@
-// 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:
-/////////////////////////////////////////////////////////////////////////
-
-
-class Identifier extends ASTNode {
-  String name;
-
-  Identifier(this.name, SourceSpan span): super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitIdentifier(this);
-
-  String toString() => name;
-}
-
-class Wildcard extends ASTNode {
-  Wildcard(SourceSpan span): super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitWildcard(this);
-
-  String toString() => '*';
-}
-
-// /*  ....   */
-class CssComment extends ASTNode {
-  String comment;
-
-  CssComment(this.comment, SourceSpan span): super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitCssComment(this);
-
-  String toString() => '/* ${comment} */';
-}
-
-// CDO/CDC (Comment Definition Open <!-- and Comment Definition Close -->).
-class CommentDefinition extends CssComment {
-  CommentDefinition(String comment, SourceSpan span): super(comment, span);
-
-  visit(TreeVisitor visitor) => visitor.visitCommentDefinition(this);
-
-  String toString() => '<!-- ${comment} -->';
-}
-
-class SelectorGroup extends ASTNode {
-  List<Selector> _selectors;
-
-  SelectorGroup(this._selectors, SourceSpan span): super(span);
-
-  List<Selector> get selectors => _selectors;
-
-  visit(TreeVisitor visitor) => visitor.visitSelectorGroup(this);
-
-  String toString() {
-    StringBuffer buff = new StringBuffer();
-    int idx = 0;
-    for (final selector in _selectors) {
-      if (idx++ > 0) {
-        buff.write(', ');
-      }
-      buff.write(selector.toString());
-    }
-    return buff.toString();
-  }
-
-  /** A multiline string showing the node and its children. */
-  String toDebugString() {
-    var to = new TreeOutput();
-    var tp = new TreePrinter(to);
-    this.visit(tp);
-    return to.buf.toString();
-  }
-}
-
-class Selector extends ASTNode {
-  List<SimpleSelectorSequence> _simpleSelectorSequences;
-
-  Selector(this._simpleSelectorSequences, SourceSpan span) : super(span);
-
-  List<SimpleSelectorSequence> get simpleSelectorSequences =>
-      _simpleSelectorSequences;
-
-  add(SimpleSelectorSequence seq) => _simpleSelectorSequences.add(seq);
-
-  List<SimpleSelectorSequence> get simpleSelectorSquences =>
-      _simpleSelectorSequences;
-
-  int get length => _simpleSelectorSequences.length;
-
-  String toString() {
-    StringBuffer buff = new StringBuffer();
-    for (final simpleSelectorSequence in _simpleSelectorSequences) {
-      buff.write(simpleSelectorSequence.toString());
-    }
-    return buff.toString();
-  }
-
-  visit(TreeVisitor visitor) => visitor.visitSelector(this);
-}
-
-class SimpleSelectorSequence extends ASTNode {
-  int _combinator;              // +, >, ~, NONE
-  SimpleSelector _selector;
-
-  SimpleSelectorSequence(this._selector, SourceSpan span,
-      [this._combinator = TokenKind.COMBINATOR_NONE]) : super(span);
-
-  get simpleSelector => _selector;
-
-  bool isCombinatorNone() => _combinator == TokenKind.COMBINATOR_NONE;
-  bool isCombinatorPlus() => _combinator == TokenKind.COMBINATOR_PLUS;
-  bool isCombinatorGreater() => _combinator == TokenKind.COMBINATOR_GREATER;
-  bool isCombinatorTilde() => _combinator == TokenKind.COMBINATOR_TILDE;
-  bool isCombinatorDescendant() =>
-      _combinator == TokenKind.COMBINATOR_DESCENDANT;
-
-  String _combinatorToString() =>
-      isCombinatorDescendant() ? ' ' :
-      isCombinatorPlus() ? '+' :
-      isCombinatorGreater() ? '>' :
-      isCombinatorTilde() ? '~' : '';
-
-  visit(TreeVisitor visitor) => visitor.visitSimpleSelectorSequence(this);
-
-  String toString() => "${_combinatorToString()}${_selector.toString()}";
-}
-
-/* All other selectors (element, #id, .class, attribute, pseudo, negation,
- * namespace, *) are derived from this selector.
- */
-class SimpleSelector extends ASTNode {
-  var _name;
-
-  SimpleSelector(this._name, SourceSpan span) : super(span);
-
-  // Name can be an Identifier or WildCard we'll return either the name or '*'.
-  String get name => isWildcard() ? '*' : _name.name;
-
-  bool isWildcard() => _name is Wildcard;
-
-  visit(TreeVisitor visitor) => visitor.visitSimpleSelector(this);
-
-  String toString() => name;
-}
-
-// element name
-class ElementSelector extends SimpleSelector {
-  ElementSelector(var name, SourceSpan span) : super(name, span);
-
-  visit(TreeVisitor visitor) => visitor.visitElementSelector(this);
-
-  String toString() => "$name";
-
-  /** A multiline string showing the node and its children. */
-  String toDebugString() {
-    var to = new TreeOutput();
-    var tp = new TreePrinter(to);
-    this.visit(tp);
-    return to.buf.toString();
-  }
-}
-
-// namespace|element
-class NamespaceSelector extends SimpleSelector {
-  var _namespace;           // null, Wildcard or Identifier
-
-  NamespaceSelector(this._namespace, var name, SourceSpan span) :
-      super(name, span);
-
-  String get namespace => _namespace is Wildcard ? '*' : _namespace.name;
-
-  bool isNamespaceWildcard() => _namespace is Wildcard;
-
-  SimpleSelector get nameAsSimpleSelector => _name;
-
-  visit(TreeVisitor visitor) => visitor.visitNamespaceSelector(this);
-
-  String toString() => "$namespace|${nameAsSimpleSelector.name}";
-}
-
-// [attr op value]
-class AttributeSelector extends SimpleSelector {
-  int _op;
-  var _value;
-
-  AttributeSelector(Identifier name, this._op, this._value,
-      SourceSpan span) : super(name, span);
-
-  String matchOperator() {
-    switch (_op) {
-    case TokenKind.EQUALS:
-      return '=';
-    case TokenKind.INCLUDES:
-      return '~=';
-    case TokenKind.DASH_MATCH:
-      return '|=';
-    case TokenKind.PREFIX_MATCH:
-      return '^=';
-    case TokenKind.SUFFIX_MATCH:
-      return '\$=';
-    case TokenKind.SUBSTRING_MATCH:
-      return '*=';
-    }
-  }
-
-  // Return the TokenKind for operator used by visitAttributeSelector.
-  String matchOperatorAsTokenString() {
-    switch (_op) {
-    case TokenKind.EQUALS:
-      return 'EQUALS';
-    case TokenKind.INCLUDES:
-      return 'INCLUDES';
-    case TokenKind.DASH_MATCH:
-      return 'DASH_MATCH';
-    case TokenKind.PREFIX_MATCH:
-      return 'PREFIX_MATCH';
-    case TokenKind.SUFFIX_MATCH:
-      return 'SUFFIX_MATCH';
-    case TokenKind.SUBSTRING_MATCH:
-      return 'SUBSTRING_MATCH';
-    }
-  }
-
-  String valueToString() {
-    if (_value is Identifier) {
-      return _value.name;
-    } else {
-      return '"${_value}"';
-    }
-  }
-
-  visit(TreeVisitor visitor) => visitor.visitAttributeSelector(this);
-
-  String toString() => "[${name} ${matchOperator()} ${valueToString()}]";
-}
-
-// #id
-class IdSelector extends SimpleSelector {
-  IdSelector(Identifier name, SourceSpan span) : super(name, span);
-
-  visit(TreeVisitor visitor) => visitor.visitIdSelector(this);
-
-  String toString() => "#$name";
-}
-
-// .class
-class ClassSelector extends SimpleSelector {
-  ClassSelector(Identifier name, SourceSpan span) : super(name, span);
-
-  visit(TreeVisitor visitor) => visitor.visitClassSelector(this);
-
-  String toString() => ".$name";
-}
-
-// :pseudoClass
-class PseudoClassSelector extends SimpleSelector {
-  PseudoClassSelector(Identifier name, SourceSpan span) :
-      super(name, span);
-
-  visit(TreeVisitor visitor) => visitor.visitPseudoClassSelector(this);
-
-  String toString() => ":$name";
-}
-
-// ::pseudoElement
-class PseudoElementSelector extends SimpleSelector {
-  PseudoElementSelector(Identifier name, SourceSpan span) :
-      super(name, span);
-
-  visit(TreeVisitor visitor) => visitor.visitPseudoElementSelector(this);
-
-  String toString() => "::$name";
-}
-
-// TODO(terry): Implement
-// NOT
-class NotSelector extends SimpleSelector {
-  NotSelector(String name, SourceSpan span) : super(name, span);
-
-  visit(TreeVisitor visitor) => visitor.visitNotSelector(this);
-}
-
-class Stylesheet extends ASTNode {
-  // Contains charset, ruleset, directives (media, page, etc.)
-  List<ASTNode> _topLevels;
-
-  Stylesheet(this._topLevels, SourceSpan span) : super(span) {
-    for (final node in _topLevels) {
-      assert(node is TopLevelProduction || node is Directive);
-    }
-  }
-
-  visit(TreeVisitor visitor) => visitor.visitStylesheet(this);
-
-  List<ASTNode> get topLevels => _topLevels;
-
-  String toString() {
-    StringBuffer buff = new StringBuffer();
-    for (final topLevel in _topLevels) {
-      buff.write(topLevel.toString());
-    }
-    return buff.toString();
-  }
-
-  /** A multiline string showing the node and its children. */
-  String toDebugString() {
-    var to = new TreeOutput();
-    var tp = new TreePrinter(to);
-    this.visit(tp);
-    return to.buf.toString();
-  }
-}
-
-class TopLevelProduction extends ASTNode {
-  TopLevelProduction(SourceSpan span) : super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitTopLevelProduction(this);
-
-  String toString() => "TopLevelProduction";
-}
-
-class RuleSet extends TopLevelProduction {
-  SelectorGroup _selectorGroup;
-  DeclarationGroup _declarationGroup;
-
-  RuleSet(this._selectorGroup, this._declarationGroup, SourceSpan span) :
-      super(span);
-
-  SelectorGroup get selectorGroup => _selectorGroup;
-  DeclarationGroup get declarationGroup => _declarationGroup;
-
-  visit(TreeVisitor visitor) => visitor.visitRuleSet(this);
-
-  String toString() =>
-      "\n${_selectorGroup.toString()} {\n"
-        "${_declarationGroup.toString()}}\n";
-}
-
-class Directive extends ASTNode {
-  Directive(SourceSpan span) : super(span);
-
-  String toString() => "Directive";
-
-  bool get isBuiltIn => true;       // Known CSS directive?
-  bool get isExtension => false;    // SCSS extension?
-
-  visit(TreeVisitor visitor) => visitor.visitDirective(this);
-}
-
-class ImportDirective extends Directive {
-  String _import;
-  List<String> _media;
-
-  ImportDirective(this._import, this._media, SourceSpan span) :
-      super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitImportDirective(this);
-
-  String toString() {
-    StringBuffer buff = new StringBuffer();
-
-    buff.write('@import url(${_import})');
-
-    int idx = 0;
-    for (final medium in _media) {
-      buff.write(idx++ == 0 ? ' $medium' : ',$medium');
-    }
-    buff.write('\n');
-
-    return buff.toString();
-  }
-}
-
-class MediaDirective extends Directive {
-  List<String> _media;
-  RuleSet _ruleset;
-
-  MediaDirective(this._media, this._ruleset, SourceSpan span) :
-      super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitMediaDirective(this);
-
-  String toString() {
-    StringBuffer buff = new StringBuffer();
-
-    buff.write('@media');
-    int idx = 0;
-    for (var medium in _media) {
-      buff.write(idx++ == 0 ? ' $medium' : ',$medium');
-    }
-    buff.write(' {\n');
-    buff.write(_ruleset.toString());
-    buff.write('\n\}\n');
-
-    return buff.toString();
-  }
-}
-
-class PageDirective extends Directive {
-  String _pseudoPage;
-  DeclarationGroup _decls;
-
-  PageDirective(this._pseudoPage, this._decls, SourceSpan span) :
-    super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitPageDirective(this);
-
-  // @page : pseudoPage {
-  //    decls
-  // }
-  String toString() {
-    StringBuffer buff = new StringBuffer();
-
-    buff.write('@page ');
-    if (_pseudoPage != null) {
-      buff.write(': ${_pseudoPage} ');
-    }
-    buff.write('{\n${_decls.toString()}\n}\n');
-
-    return buff.toString();
-  }
-}
-
-class KeyFrameDirective extends Directive {
-  var _name;
-  List<KeyFrameBlock> _blocks;
-
-  KeyFrameDirective(this._name, SourceSpan span) :
-      _blocks = [], super(span);
-
-  add(KeyFrameBlock block) {
-    _blocks.add(block);
-  }
-
-  String get name => _name;
-
-  visit(TreeVisitor visitor) => visitor.visitKeyFrameDirective(this);
-
-  String toString() {
-    StringBuffer buff = new StringBuffer();
-    buff.write('@-webkit-keyframes ${_name} {\n');
-    for (final block in _blocks) {
-      buff.write(block.toString());
-    }
-    buff.write('}\n');
-    return buff.toString();
-  }
-}
-
-class KeyFrameBlock extends Expression {
-  Expressions _blockSelectors;
-  DeclarationGroup _declarations;
-
-  KeyFrameBlock(this._blockSelectors, this._declarations, SourceSpan span):
-      super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitKeyFrameBlock(this);
-
-  String toString() {
-    StringBuffer buff = new StringBuffer();
-    buff.write('  ${_blockSelectors.toString()} {\n');
-    buff.write(_declarations.toString());
-    buff.write('  }\n');
-    return buff.toString();
-  }
-}
-
-// TODO(terry): TBD
-class FontFaceDirective extends Directive {
-  List<Declaration> _declarations;
-
-  FontFaceDirective(this._declarations, SourceSpan span) : super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitFontFaceDirective(this);
-
-  String toString() {
-    return "TO BE DONE";
-  }
-}
-
-class IncludeDirective extends Directive {
-  String _include;
-  Stylesheet _stylesheet;
-
-  IncludeDirective(this._include, this._stylesheet, SourceSpan span) :
-      super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitIncludeDirective(this);
-
-  bool get isBuiltIn => false;
-  bool get isExtension => true;
-
-  Stylesheet get styleSheet => _stylesheet;
-
-  String toString() {
-    StringBuffer buff = new StringBuffer();
-    buff.write('/****** @include ${_include} ******/\n');
-    buff.write(_stylesheet != null ? _stylesheet.toString() : '// <EMPTY>');
-    buff.write('/****** End of ${_include} ******/\n\n');
-    return buff.toString();
-  }
-}
-
-class StyletDirective extends Directive {
-  String _dartClassName;
-  List<RuleSet> _rulesets;
-
-  StyletDirective(this._dartClassName, this._rulesets, SourceSpan span) :
-      super(span);
-
-  bool get isBuiltIn => false;
-  bool get isExtension => true;
-
-  String get dartClassName => _dartClassName;
-  List<RuleSet> get rulesets => _rulesets;
-
-  visit(TreeVisitor visitor) => visitor.visitStyletDirective(this);
-
-  // TODO(terry): Output Dart class
-  String toString() => '/* @stylet export as ${_dartClassName} */\n';
-}
-
-class Declaration extends ASTNode {
-  Identifier _property;
-  Expression _expression;
-  bool _important;
-
-  Declaration(this._property, this._expression, SourceSpan span) :
-      _important = false, super(span);
-
-  String get property => _property.name;
-  Expression get expression => _expression;
-
-  bool get important => _important;
-  set important(bool value) => _important = value;
-  String importantAsString() => _important ? ' !important' : '';
-
-  visit(TreeVisitor visitor) => visitor.visitDeclaration(this);
-
-  String toString() =>
-      "${_property.name}: ${_expression.toString()}${importantAsString()}";
-}
-
-class DeclarationGroup extends ASTNode {
-  List<Declaration> _declarations;
-
-  DeclarationGroup(this._declarations, SourceSpan span) : super(span);
-
-  List<Declaration> get declarations => _declarations;
-
-  visit(TreeVisitor visitor) => visitor.visitDeclarationGroup(this);
-
-  String toString() {
-    StringBuffer buff = new StringBuffer();
-    int idx = 0;
-    for (final declaration in _declarations) {
-      buff.write("  ${declaration.toString()};\n");
-    }
-    return buff.toString();
-  }
-}
-
-class OperatorSlash extends Expression {
-  OperatorSlash(SourceSpan span) : super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitOperatorSlash(this);
-
-  String toString() => ' /';
-}
-
-class OperatorComma extends Expression {
-  OperatorComma(SourceSpan span) : super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitOperatorComma(this);
-
-  String toString() => ',';
-}
-
-class LiteralTerm extends Expression {
-  var _value;
-  String _text;
-
-  LiteralTerm(this._value, this._text, SourceSpan span) : super(span);
-
-  get value => _value;
-  String get text => _text;
-
-  visit(TreeVisitor visitor) => visitor.visitLiteralTerm(this);
-
-  String toString() => _text;
-}
-
-class NumberTerm extends LiteralTerm {
-  NumberTerm(var value, String t, SourceSpan span) : super(value, t, span);
-
-  visit(TreeVisitor visitor) => visitor.visitNumberTerm(this);
-}
-
-class UnitTerm extends LiteralTerm {
-  int _unit;
-
-  UnitTerm(var value, String t, SourceSpan span, this._unit) :
-      super(value, t, span);
-
-  int get unit => _unit;
-
-  visit(TreeVisitor visitor) => visitor.visitUnitTerm(this);
-
-  String toString() => '${text}${unitToString()}';
-  String unitToString() => TokenKind.unitToString(_unit);
-}
-
-class LengthTerm extends UnitTerm {
-  LengthTerm(var value, String t, SourceSpan span,
-      [int unit = TokenKind.UNIT_LENGTH_PX]) : super(value, t, span, unit) {
-    assert(this._unit == TokenKind.UNIT_LENGTH_PX ||
-        this._unit == TokenKind.UNIT_LENGTH_CM ||
-        this._unit == TokenKind.UNIT_LENGTH_MM ||
-        this._unit == TokenKind.UNIT_LENGTH_IN ||
-        this._unit == TokenKind.UNIT_LENGTH_PT ||
-        this._unit == TokenKind.UNIT_LENGTH_PC);
-  }
-
-  visit(TreeVisitor visitor) => visitor.visitLengthTerm(this);
-}
-
-class PercentageTerm extends LiteralTerm {
-  PercentageTerm(var value, String t, SourceSpan span) :
-      super(value, t, span);
-
-  visit(TreeVisitor visitor) => visitor.visitPercentageTerm(this);
-
-  String toString() => '${text}%';
-
-}
-
-class EmTerm extends LiteralTerm {
-  EmTerm(var value, String t, SourceSpan span) :
-      super(value, t, span);
-
-  visit(TreeVisitor visitor) => visitor.visitEmTerm(this);
-
-  String toString() => '${text}em';
-}
-
-class ExTerm extends LiteralTerm {
-  ExTerm(var value, String t, SourceSpan span) :
-      super(value, t, span);
-
-  visit(TreeVisitor visitor) => visitor.visitExTerm(this);
-
-  String toString() => '${text}ex';
-}
-
-class AngleTerm extends UnitTerm {
-  AngleTerm(var value, String t, SourceSpan span,
-    [int unit = TokenKind.UNIT_LENGTH_PX]) : super(value, t, span, unit) {
-    assert(this._unit == TokenKind.UNIT_ANGLE_DEG ||
-        this._unit == TokenKind.UNIT_ANGLE_RAD ||
-        this._unit == TokenKind.UNIT_ANGLE_GRAD);
-  }
-
-  visit(TreeVisitor visitor) => visitor.visitAngleTerm(this);
-}
-
-class TimeTerm extends UnitTerm {
-  TimeTerm(var value, String t, SourceSpan span,
-    [int unit = TokenKind.UNIT_LENGTH_PX]) : super(value, t, span, unit) {
-    assert(this._unit == TokenKind.UNIT_ANGLE_DEG ||
-        this._unit == TokenKind.UNIT_TIME_MS ||
-        this._unit == TokenKind.UNIT_TIME_S);
-  }
-
-  visit(TreeVisitor visitor) => visitor.visitTimeTerm(this);
-}
-
-class FreqTerm extends UnitTerm {
-  FreqTerm(var value, String t, SourceSpan span,
-    [int unit = TokenKind.UNIT_LENGTH_PX]) : super(value, t, span, unit) {
-    assert(_unit == TokenKind.UNIT_FREQ_HZ || _unit == TokenKind.UNIT_FREQ_KHZ);
-  }
-
-  visit(TreeVisitor visitor) => visitor.visitFreqTerm(this);
-}
-
-class FractionTerm extends LiteralTerm {
-  FractionTerm(var value, String t, SourceSpan span) :
-    super(value, t, span);
-
-  visit(TreeVisitor visitor) => visitor.visitFractionTerm(this);
-
-  String toString() => '${text}fr';
-}
-
-class UriTerm extends LiteralTerm {
-  UriTerm(String value, SourceSpan span) : super(value, value, span);
-
-  visit(TreeVisitor visitor) => visitor.visitUriTerm(this);
-
-  String toString() => 'url(${text})';
-}
-
-class HexColorTerm extends LiteralTerm {
-  HexColorTerm(var value, String t, SourceSpan span) :
-      super(value, t, span);
-
-  visit(TreeVisitor visitor) => visitor.visitHexColorTerm(this);
-
-  String toString() => '#${text}';
-}
-
-class FunctionTerm extends LiteralTerm {
-  Expressions _params;
-
-  FunctionTerm(var value, String t, this._params, SourceSpan span)
-      : super(value, t, span);
-
-  visit(TreeVisitor visitor) => visitor.visitFunctionTerm(this);
-
-  String toString() {
-    // TODO(terry): Optimize rgb to a hexcolor.
-    StringBuffer buff = new StringBuffer();
-
-    buff.write('${text}(');
-    buff.write(_params.toString());
-    buff.write(')');
-
-    return buff.toString();
-  }
-}
-
-class GroupTerm extends Expression {
-  List<LiteralTerm> _terms;
-
-  GroupTerm(SourceSpan span) : _terms =  [], super(span);
-
-  add(LiteralTerm term) {
-    _terms.add(term);
-  }
-
-  visit(TreeVisitor visitor) => visitor.visitGroupTerm(this);
-
-  String toString() {
-    StringBuffer buff = new StringBuffer();
-    buff.write('(');
-    int idx = 0;
-    for (final term in _terms) {
-      if (idx++ > 0) {
-        buff.write(' ');
-      }
-      buff.write(term.toString());
-    }
-    buff.write(')');
-    return buff.toString();
-  }
-}
-
-class ItemTerm extends NumberTerm {
-  ItemTerm(var value, String t, SourceSpan span) : super(value, t, span);
-
-  visit(TreeVisitor visitor) => visitor.visitItemTerm(this);
-
-  String toString() => '[${text}]';
-}
-
-class Expressions extends Expression {
-  List<Expression> _expressions;
-
-  Expressions(SourceSpan span): super(span), _expressions = [];
-
-  add(Expression expression) {
-    _expressions.add(expression);
-  }
-
-  List<Expression> get expressions => _expressions;
-
-  visit(TreeVisitor visitor) => visitor.visitExpressions(this);
-
-  String toString() {
-    StringBuffer buff = new StringBuffer();
-    int idx = 0;
-    for (final expression in _expressions) {
-      // Add space seperator between terms without an operator.
-      // TODO(terry): Should have a BinaryExpression to solve this problem.
-      if (idx > 0 &&
-          !(expression is OperatorComma || expression is OperatorSlash)) {
-        buff.write(' ');
-      }
-      buff.write(expression.toString());
-      idx++;
-    }
-    return buff.toString();
-  }
-}
-
-class BinaryExpression extends Expression {
-  Token op;
-  Expression x;
-  Expression y;
-
-  BinaryExpression(this.op, this.x, this.y, SourceSpan span): super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitBinaryExpression(this);
-}
-
-class UnaryExpression extends Expression {
-  Token op;
-  Expression self;
-
-  UnaryExpression(this.op, this.self, SourceSpan span): super(span);
-
-  visit(TreeVisitor visitor) => visitor.visitUnaryExpression(this);
-}
-
-abstract class TreeVisitor {
-  void visitCssComment(CssComment node);
-  void visitCommentDefinition(CommentDefinition node);
-  void visitStylesheet(Stylesheet node);
-  void visitTopLevelProduction(TopLevelProduction node);
-  void visitDirective(Directive node);
-  void visitMediaDirective(MediaDirective node);
-  void visitPageDirective(PageDirective node);
-  void visitImportDirective(ImportDirective node);
-  void visitKeyFrameDirective(KeyFrameDirective node);
-  void visitKeyFrameBlock(KeyFrameBlock node);
-  void visitFontFaceDirective(FontFaceDirective node);
-  void visitIncludeDirective(IncludeDirective node);
-  void visitStyletDirective(StyletDirective node);
-
-  void visitRuleSet(RuleSet node);
-  void visitDeclarationGroup(DeclarationGroup node);
-  void visitDeclaration(Declaration node);
-  void visitSelectorGroup(SelectorGroup node);
-  void visitSelector(Selector node);
-  void visitSimpleSelectorSequence(SimpleSelectorSequence node);
-  void visitSimpleSelector(SimpleSelector node);
-  void visitElementSelector(ElementSelector node);
-  void visitNamespaceSelector(NamespaceSelector node);
-  void visitAttributeSelector(AttributeSelector node);
-  void visitIdSelector(IdSelector node);
-  void visitClassSelector(ClassSelector node);
-  void visitPseudoClassSelector(PseudoClassSelector node);
-  void visitPseudoElementSelector(PseudoElementSelector node);
-  void visitNotSelector(NotSelector node);
-
-  void visitLiteralTerm(LiteralTerm node);
-  void visitHexColorTerm(HexColorTerm node);
-  void visitNumberTerm(NumberTerm node);
-  void visitUnitTerm(UnitTerm node);
-  void visitLengthTerm(LengthTerm node);
-  void visitPercentageTerm(PercentageTerm node);
-  void visitEmTerm(EmTerm node);
-  void visitExTerm(ExTerm node);
-  void visitAngleTerm(AngleTerm node);
-  void visitTimeTerm(TimeTerm node);
-  void visitFreqTerm(FreqTerm node);
-  void visitFractionTerm(FractionTerm node);
-  void visitUriTerm(UriTerm node);
-  void visitFunctionTerm(FunctionTerm node);
-  void visitGroupTerm(GroupTerm node);
-  void visitItemTerm(ItemTerm node);
-  void visitOperatorSlash(OperatorSlash node);
-  void visitOperatorComma(OperatorComma node);
-
-  void visitExpressions(Expressions node);
-  void visitBinaryExpression(BinaryExpression node);
-  void visitUnaryExpression(UnaryExpression node);
-
-  void visitIdentifier(Identifier node);
-  void visitWildcard(Wildcard node);
-
-  // TODO(terry): Defined for ../tree.dart.
-  void visitTypeReference(TypeReference node);
-}
-
-class TreePrinter implements TreeVisitor {
-  var output;
-  TreePrinter(this.output) { output.printer = this; }
-
-  void visitStylesheet(Stylesheet node) {
-    output.heading('Stylesheet', node.span);
-    output.depth++;
-    output.writeNodeList('productions', node._topLevels);
-    output.depth--;
-  }
-
-  void visitTopLevelProduction(TopLevelProduction node) {
-    output.heading('TopLevelProduction', node.span);
-  }
-
-  void visitDirective(Directive node) {
-    output.heading('Directive', node.span);
-  }
-
-  void visitCssComment(CssComment node) {
-    output.heading('Comment', node.span);
-    output.depth++;
-    output.writeValue('comment value', node.comment);
-    output.depth--;
-  }
-
-  void visitCommentDefinition(CommentDefinition node) {
-    output.heading('CommentDefinition (CDO/CDC)', node.span);
-    output.depth++;
-    output.writeValue('comment value', node.comment);
-    output.depth--;
-  }
-
-  void visitMediaDirective(MediaDirective node) {
-    output.heading('MediaDirective', node.span);
-    output.depth++;
-    output.writeNodeList('media', node._media);
-    visitRuleSet(node._ruleset);
-    output.depth--;
-  }
-
-  void visitPageDirective(PageDirective node) {
-    output.heading('PageDirective', node.span);
-    output.depth++;
-    output.writeValue('pseudo page', node._pseudoPage);
-    visitDeclarationGroup(node._decls);
-    output.depth;
-}
-
-  void visitImportDirective(ImportDirective node) {
-    output.heading('ImportDirective', node.span);
-    output.depth++;
-    output.writeValue('import', node._import);
-    output.writeNodeList('media', node._media);
-    output.depth--;
-  }
-
-  void visitKeyFrameDirective(KeyFrameDirective node) {
-    output.heading('KeyFrameDirective', node.span);
-    output.depth++;
-    output.writeValue('name', node._name);
-    output.writeNodeList('blocks', node._blocks);
-    output.depth--;
-  }
-
-  void visitKeyFrameBlock(KeyFrameBlock node) {
-    output.heading('KeyFrameBlock', node.span);
-    output.depth++;
-    visitExpressions(node._blockSelectors);
-    visitDeclarationGroup(node._declarations);
-    output.depth--;
-  }
-
-  void visitFontFaceDirective(FontFaceDirective node) {
-    // TODO(terry): To Be Implemented
-  }
-
-  void visitIncludeDirective(IncludeDirective node) {
-    output.heading('IncludeDirective', node.span);
-    output.writeValue('include', node._include);
-    output.depth++;
-    if (node._stylesheet != null) {
-      visitStylesheet(node._stylesheet);
-    } else {
-      output.writeValue('StyleSheet', '<EMPTY>');
-    }
-    output.depth--;
-  }
-
-  void visitStyletDirective(StyletDirective node) {
-    output.heading('StyletDirective', node.span);
-    output.writeValue('dartClassName', node._dartClassName);
-    output.depth++;
-    output.writeNodeList('rulesets', node._rulesets);
-    output.depth--;
-}
-
-  void visitRuleSet(RuleSet node) {
-    output.heading('Ruleset', node.span);
-    output.depth++;
-    visitSelectorGroup(node._selectorGroup);
-    visitDeclarationGroup(node._declarationGroup);
-    output.depth--;
-  }
-
-  void visitDeclarationGroup(DeclarationGroup node) {
-    output.heading('DeclarationGroup', node.span);
-    output.depth++;
-    output.writeNodeList('declarations', node._declarations);
-    output.depth--;
-  }
-
-  void visitDeclaration(Declaration node) {
-    output.heading('Declaration', node.span);
-    output.depth++;
-    output.write('property');
-    visitIdentifier(node._property);
-    output.writeNode('expression', node._expression);
-    if (node.important) {
-      output.writeValue('!important', 'true');
-    }
-    output.depth--;
-  }
-
-  void visitSelectorGroup(SelectorGroup node) {
-    output.heading('Selector Group', node.span);
-    output.depth++;
-    output.writeNodeList('selectors', node.selectors);
-    output.depth--;
-  }
-
-  void visitSelector(Selector node) {
-    output.heading('Selector', node.span);
-    output.depth++;
-    output.writeNodeList('simpleSelectorsSequences',
-        node._simpleSelectorSequences);
-    output.depth--;
-  }
-
-  void visitSimpleSelectorSequence(SimpleSelectorSequence node) {
-    output.heading('SimpleSelectorSequence', node.span);
-    output.depth++;
-    if (node.isCombinatorNone()) {
-      output.writeValue('combinator', "NONE");
-    } else if (node.isCombinatorDescendant()) {
-      output.writeValue('combinator', "descendant");
-    } else if (node.isCombinatorPlus()) {
-      output.writeValue('combinator', "+");
-    } else if (node.isCombinatorGreater()) {
-      output.writeValue('combinator', ">");
-    } else if (node.isCombinatorTilde()) {
-      output.writeValue('combinator', "~");
-    } else {
-      output.writeValue('combinator', "ERROR UNKNOWN");
-    }
-
-    var selector = node._selector;
-    if (selector is NamespaceSelector) {
-      visitNamespaceSelector(selector);
-    } else if (selector is ElementSelector) {
-      visitElementSelector(selector);
-    } else if (selector is IdSelector) {
-      visitIdSelector(selector);
-    } else if (selector is ClassSelector) {
-      visitClassSelector(selector);
-    } else if (selector is PseudoClassSelector) {
-      visitPseudoClassSelector(selector);
-    } else if (selector is PseudoElementSelector) {
-      visitPseudoElementSelector(selector);
-    } else if (selector is NotSelector) {
-      visitNotSelector(selector);
-    } else if (selector is AttributeSelector) {
-      visitAttributeSelector(selector);
-    } else {
-      output.heading('SimpleSelector', selector.span);
-      output.depth++;
-      visitSimpleSelector(selector);
-      output.depth--;
-    }
-
-    output.depth--;
-  }
-
-  void visitSimpleSelector(SimpleSelector node) {
-    visitIdentifier(node._name);
-  }
-
-  void visitNamespaceSelector(NamespaceSelector node) {
-    output.heading('Namespace Selector', node.span);
-    output.depth++;
-
-    var namespace = node._namespace;
-    if (namespace is Identifier) {
-      visitIdentifier(namespace);
-    } else if (namespace is Wildcard) {
-      visitWildcard(namespace);
-    } else {
-      output.writeln("NULL");
-    }
-
-    visitSimpleSelector(node.nameAsSimpleSelector);
-    output.depth--;
-  }
-
-  void visitElementSelector(ElementSelector node) {
-    output.heading('Element Selector', node.span);
-    output.depth++;
-    visitSimpleSelector(node);
-    output.depth--;
-  }
-
-  void visitAttributeSelector(AttributeSelector node) {
-    output.heading('AttributeSelector', node.span);
-    output.depth++;
-    visitSimpleSelector(node);
-    String tokenStr = node.matchOperatorAsTokenString();
-    output.writeValue('operator', '${node.matchOperator()} (${tokenStr})');
-    output.writeValue('value', node.valueToString());
-    output.depth--;
-  }
-
-  void visitIdSelector(IdSelector node) {
-    output.heading('Id Selector', node.span);
-    output.depth++;
-    visitSimpleSelector(node);
-    output.depth--;
-  }
-
-  void visitClassSelector(ClassSelector node) {
-    output.heading('Class Selector', node.span);
-    output.depth++;
-    visitSimpleSelector(node);
-    output.depth--;
-  }
-
-  void visitPseudoClassSelector(PseudoClassSelector node) {
-    output.heading('Pseudo Class Selector', node.span);
-    output.depth++;
-    visitSimpleSelector(node);
-    output.depth--;
-  }
-
-  void visitPseudoElementSelector(PseudoElementSelector node) {
-    output.heading('Pseudo Element Selector', node.span);
-    output.depth++;
-    visitSimpleSelector(node);
-    output.depth--;
-  }
-
-  void visitNotSelector(NotSelector node) {
-    visitSimpleSelector(node);
-    output.depth++;
-    output.heading('Not Selector', node.span);
-    output.depth--;
-  }
-
-  void visitLiteralTerm(LiteralTerm node) {
-    output.heading('LiteralTerm', node.span);
-    output.depth++;
-    output.writeValue('value', node.text);
-    output.depth--;
- }
-
-  void visitHexColorTerm(HexColorTerm node) {
-    output.heading('HexColorTerm', node.span);
-    output.depth++;
-    output.writeValue('hex value', node.text);
-    output.writeValue('decimal value', node.value);
-    output.depth--;
-  }
-
-  void visitNumberTerm(NumberTerm node) {
-    output.heading('NumberTerm', node.span);
-    output.depth++;
-    output.writeValue('value', node.text);
-    output.depth--;
-  }
-
-  void visitUnitTerm(UnitTerm node) {
-    String unitValue;
-
-    output.depth++;
-    output.writeValue('value', node.text);
-    output.writeValue('unit', node.unitToString());
-    output.depth--;
-  }
-
-  void visitLengthTerm(LengthTerm node) {
-    output.heading('LengthTerm', node.span);
-    visitUnitTerm(node);
-  }
-
-  void visitPercentageTerm(PercentageTerm node) {
-    output.heading('PercentageTerm', node.span);
-    output.depth++;
-    visitLiteralTerm(node);
-    output.depth--;
-  }
-
-  void visitEmTerm(EmTerm node) {
-    output.heading('EmTerm', node.span);
-    output.depth++;
-    visitLiteralTerm(node);
-    output.depth--;
-  }
-
-  void visitExTerm(ExTerm node) {
-    output.heading('ExTerm', node.span);
-    output.depth++;
-    visitLiteralTerm(node);
-    output.depth--;
-  }
-
-  void visitAngleTerm(AngleTerm node) {
-    output.heading('AngleTerm', node.span);
-    visitUnitTerm(node);
-  }
-
-  void visitTimeTerm(TimeTerm node) {
-    output.heading('TimeTerm', node.span);
-    visitUnitTerm(node);
-  }
-
-  void visitFreqTerm(FreqTerm node) {
-    output.heading('FreqTerm', node.span);
-    visitUnitTerm(node);
-  }
-
-  void visitFractionTerm(FractionTerm node) {
-    output.heading('FractionTerm', node.span);
-    output.depth++;
-    visitLiteralTerm(node);
-    output.depth--;
-  }
-
-  void visitUriTerm(UriTerm node) {
-    output.heading('UriTerm', node.span);
-    output.depth++;
-    visitLiteralTerm(node);
-    output.depth--;
-  }
-
-  void visitFunctionTerm(FunctionTerm node) {
-    output.heading('FunctionTerm', node.span);
-    output.depth++;
-    visitLiteralTerm(node);
-    visitExpressions(node._params);
-    output.depth--;
-  }
-
-  void visitGroupTerm(GroupTerm node) {
-    output.heading('GroupTerm', node.span);
-    output.depth++;
-    output.writeNodeList('grouped terms', node._terms);
-    output.depth--;
-  }
-
-  void visitItemTerm(ItemTerm node) {
-    output.heading('ItemTerm', node.span);
-    visitNumberTerm(node);
-  }
-
-  void visitOperatorSlash(OperatorSlash node) {
-    output.heading('OperatorSlash', node.span);
-  }
-
-  void visitOperatorComma(OperatorComma node) {
-    output.heading('OperatorComma', node.span);
-  }
-
-  void visitExpressions(Expressions node) {
-    output.heading('Expressions', node.span);
-    output.depth++;
-    output.writeNodeList('expressions', node._expressions);
-    output.depth--;
-  }
-
-  void visitBinaryExpression(BinaryExpression node) {
-    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);
-  }
-
-  void visitWildcard(Wildcard node) {
-    output.heading('Wildcard(*)', node.span);
-  }
-
-  // TODO(terry): Defined for frog/tree.dart.
-  void visitTypeReference(TypeReference node) {
-    output.heading('Unimplemented');
-  }
-}