dart2js: Pass type information to constructor rather than add later.

pkg/compiler/lib/src/js_emitter/class_stub_generator.dart

Index: pkg/compiler/lib/src/js_emitter/class_stub_generator.dart
diff --git a/pkg/compiler/lib/src/js_emitter/class_stub_generator.dart b/pkg/compiler/lib/src/js_emitter/class_stub_generator.dart
index 447710dca781f2ef0320f282ad342a15fc5cd94f..d07c36fa1a4623f14139c6894447e0edd2a5c8ec 100644
--- a/pkg/compiler/lib/src/js_emitter/class_stub_generator.dart
+++ b/pkg/compiler/lib/src/js_emitter/class_stub_generator.dart
@@ -11,8 +11,8 @@ class ClassStubGenerator {
 
   ClassStubGenerator(this.compiler, this.namer, this.backend);
 
-  jsAst.Expression generateClassConstructor(
-      ClassElement classElement, Iterable<jsAst.Name> fields) {
+  jsAst.Expression generateClassConstructor(ClassElement classElement,
+      Iterable<jsAst.Name> fields, bool hasRtiField) {
     // TODO(sra): Implement placeholders in VariableDeclaration position:
     //
     //     String constructorName = namer.getNameOfClass(classElement);
@@ -20,9 +20,18 @@ class ClassStubGenerator {
     //        [ constructorName, fields,
     //            fields.map(
     //                (name) => js('this.# = #', [name, name]))]));
-    return js('function(#) { #; this.#();}', [
+    var typeParameters = const <jsAst.Parameter>[];
+    var typeInits = const <jsAst.Expression>[];
+    if (hasRtiField) {
+      String parameterName = r'$ti';
+      typeParameters = parameterName;
+      typeInits = js('this.# = #', [namer.rtiFieldName, parameterName]);
+    }
+    return js('function(#, #) { #; #; this.#();}', [
       fields,
+      typeParameters,
       fields.map((name) => js('this.# = #', [name, name])),
+      typeInits,
       namer.deferredAction
     ]);
   }