Implement CssNode.toString() using toCss().

lib/src/ast/css/comment.dart

@@ -15,6 +15,4 @@ class CssComment extends CssNode {
   CssComment(this.text, this.span);
 
   /*=T*/ accept/*<T>*/(CssVisitor/*<T>*/ visitor) => visitor.visitComment(this);
-
-  String toString() => text;
 }

lib/src/ast/css/declaration.dart

@@ -22,6 +22,4 @@ class CssDeclaration extends CssNode {
 
   /*=T*/ accept/*<T>*/(CssVisitor/*<T>*/ visitor) =>
       visitor.visitDeclaration(this);
-
-  String toString() => "$name: $value;";
 }

lib/src/ast/css/media_query.dart

@@ -72,16 +72,4 @@ class CssMediaQuery implements AstNode {
         modifier: modifier == ourModifier ? this.modifier : other.modifier,
         features: features.toList()..addAll(other.features));
   }
-
-  String toString() {
-    var buffer = new StringBuffer();
-    if (modifier != null) buffer.write("$modifier ");
-    if (type != null) {
-      buffer.write(type);
-      if (features.isNotEmpty) buffer.write(" and ");
-    }
-
-    buffer.write(features.join(" and "));
-    return buffer.toString();
-  }
 }

lib/src/ast/css/node.dart

@@ -5,6 +5,7 @@
 import 'dart:collection';
 
 import '../../visitor/interface/css.dart';
+import '../../visitor/serialize.dart';
 import '../node.dart';
 
 abstract class CssNode extends AstNode {
@@ -25,6 +26,8 @@ abstract class CssNode extends AstNode {
       _parent._children[i]._indexInParent--;
     }
   }
+
+  String toString() => toCss(this);
 }
 
 // New at-rule implementations should add themselves to at-root's exclude logic.

lib/src/ast/css/style_rule.dart

@@ -20,6 +20,4 @@ class CssStyleRule extends CssParentNode {
       visitor.visitStyleRule(this);
 
   CssStyleRule copyWithoutChildren() => new CssStyleRule(selector, span);
-
-  String toString() => "$selector {${children.join(" ")}}";
 }

lib/src/ast/css/stylesheet.dart

@@ -16,6 +16,4 @@ class CssStylesheet extends CssParentNode {
       visitor.visitStylesheet(this);
 
   CssStylesheet copyWithoutChildren() => new CssStylesheet(span);
-
-  String toString() => children.join(" ");
 }

lib/src/ast/css/value.dart

@@ -12,6 +12,4 @@ class CssValue<T> implements AstNode {
   final FileSpan span;
 
   CssValue(this.value, this.span);
-
-  String toString() => value.toString();
 }