Changed interfaces to abstract classes in utils.

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 206 matching lines @@
     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);
 
@@ skipping 52 matching lines @@
 
   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.add(topLevel.toString());
     }
     return buff.toString();
   }
 
   /** A multiline string showing the node and its children. */
   String toDebugString() {
@@ skipping 382 matching lines @@
 
   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);
@@ skipping 86 matching lines @@
 
 class UnaryExpression extends Expression {
   Token op;
   Expression self;
 
   UnaryExpression(this.op, this.self, SourceSpan span): super(span);
 
   visit(TreeVisitor visitor) => visitor.visitUnaryExpression(this);
 }
 
-interface TreeVisitor {
+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);
@@ skipping 79 matching lines @@
     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);    
+    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);
@@ skipping 208 matching lines @@
     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++;
@@ skipping 81 matching lines @@
 
   void visitWildcard(Wildcard node) {
     output.heading('Wildcard(*)', node.span);
   }
 
   // TODO(terry): Defined for frog/tree.dart.
   void visitTypeReference(TypeReference node) {
     output.heading('Unimplemented');
   }
 }