dart2js: Use an abstract Name class for names in the generated JavaScript ast.

pkg/js_ast/lib/src/builder.dart

 // Copyright (c) 2013, 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.
 
 // Utilities for building JS ASTs at runtime.  Contains a builder class
 // and a parser that parses part of the language.
 
 part of js_ast;
 
 
@@ skipping 334 matching lines @@
     } else {
       _parts = new List.from(parts, growable: false);
     }
     return new StringConcatenation(_parts);
   }
 
   Iterable<Literal> joinLiterals(Iterable<Literal> list, Literal separator) {
     return new _InterleaveIterable(list, separator);
   }
 
+  LiteralString quoteName(Name name, {allowNull: false}) {
+    if (name == null) {
+      assert(allowNull);
+      return new LiteralString('""');
+    }
+    return new LiteralStringFromName(name);
+  }
+
   LiteralNumber number(num value) => new LiteralNumber('$value');
 
   LiteralBool boolean(bool value) => new LiteralBool(value);
 
   ArrayInitializer numArray(Iterable<int> list) =>
       new ArrayInitializer(list.map(number).toList());
 
   ArrayInitializer stringArray(Iterable<String> list) =>
       new ArrayInitializer(list.map(string).toList());
 
   Comment comment(String text) => new Comment(text);
 
   Call propertyCall(Expression receiver,
-                      String fieldName,
-                      List<Expression> arguments) {
-    return new Call(new PropertyAccess.field(receiver, fieldName), arguments);
+                    Expression fieldName,
+                    List<Expression> arguments) {
+    return new Call(new PropertyAccess(receiver, fieldName), arguments);
   }
 }
 
 LiteralString string(String value) => js.string(value);
+LiteralString quoteName(Name name, {allowNull: false}) {
+  return js.quoteName(name, allowNull: allowNull);
+}
 LiteralString stringPart(String value) => js.stringPart(value);
 Iterable<Literal> joinLiterals(Iterable<Literal> list, Literal separator) {
   return js.joinLiterals(list, separator);
 }
+StringConcatenation concatenateStrings(Iterable<Literal> parts,
+                                       {addQuotes: false}) {
+  return js.concatenateStrings(parts, addQuotes: addQuotes);
+}
+
 LiteralNumber number(num value) => js.number(value);
 ArrayInitializer numArray(Iterable<int> list) => js.numArray(list);
 ArrayInitializer stringArray(Iterable<String> list) => js.stringArray(list);
 Call propertyCall(Expression receiver,
-                  String fieldName,
+                  Expression fieldName,
                   List<Expression> arguments) {
   return js.propertyCall(receiver, fieldName, arguments);
 }
 
 class MiniJsParserError {
   MiniJsParserError(this.parser, this.message) { }
 
   final MiniJsParser parser;
   final String message;
 
@@ skipping 1009 matching lines @@
 class _InterleaveIterable extends IterableBase {
   Iterable<Node> source;
   Node separator;
 
   _InterleaveIterable(this.source, this.separator);
 
   Iterator<Node> get iterator {
     return new _InterleaveIterator(source.iterator, separator);
   }
 }