dart2js: Construct the entire output as a single AST before printing.

pkg/compiler/lib/src/js_backend/constant_emitter.dart

 // Copyright (c) 2012, 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.
 
 part of js_backend;
 
 typedef jsAst.Expression _ConstantReferenceGenerator(ConstantValue constant);
 
 /**
  * Generates the JavaScript expressions for constants.
@@ skipping 278 matching lines @@
     return rawJavaScript.replaceAll(COMMENT_RE, '');
   }
 
   jsAst.Expression maybeAddTypeArguments(InterfaceType type,
                                          jsAst.Expression value) {
     if (type is InterfaceType &&
         !type.treatAsRaw &&
         backend.classNeedsRti(type.element)) {
       InterfaceType interface = type;
       RuntimeTypes rti = backend.rti;
-      Iterable<String> arguments = interface.typeArguments
+      Iterable<jsAst.Expression> arguments = interface.typeArguments
           .map((DartType type) =>
-              rti.getTypeRepresentationWithHashes(type, (_){}));
+              rti.getTypeRepresentationWithPlaceholders(type, (_){}));
       jsAst.Expression argumentList =
-          new jsAst.LiteralString('[${arguments.join(', ')}]');
+          new jsAst.ArrayInitializer(arguments.toList());
       return new jsAst.Call(getHelperProperty(backend.getSetRuntimeTypeInfo()),
                             [value, argumentList]);
     }
     return value;
   }
 
   @override
   jsAst.Expression visitDeferred(DeferredConstantValue constant, [_]) {
     return constantReferenceGenerator(constant.referenced);
   }
 }