Record names of constructors and use that to implement Object.toString.

dart/frog/leg/emitter.dart

Index: dart/frog/leg/emitter.dart
diff --git a/dart/frog/leg/emitter.dart b/dart/frog/leg/emitter.dart
index 30a3df24a01553fea6bff61f390b4e6d6989d0cf..3e2d3c8c292ef2887cc5562894851e145b3d461e 100644
--- a/dart/frog/leg/emitter.dart
+++ b/dart/frog/leg/emitter.dart
@@ -100,7 +100,7 @@ function(child, parent) {
     }
 
     String className = namer.isolatePropertyAccess(classElement);
-    buffer.add('$className = function(');
+    buffer.add('$className = function ${classElement.name}(');
     StringBuffer bodyBuffer = new StringBuffer();
     generateFieldInits(classElement, buffer, bodyBuffer);
     buffer.add(') {\n');