dart2js: Add "onlyForRti" to Classes in model of the new emitter.

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

Index: pkg/compiler/lib/src/js_emitter/program_builder.dart
diff --git a/pkg/compiler/lib/src/js_emitter/program_builder.dart b/pkg/compiler/lib/src/js_emitter/program_builder.dart
index 3738340a2d96e84ee7983bc1ee65e63d613ea701..a348f4014be5eec23efa69018853ac7e64e6b8d0 100644
--- a/pkg/compiler/lib/src/js_emitter/program_builder.dart
+++ b/pkg/compiler/lib/src/js_emitter/program_builder.dart
@@ -264,7 +264,10 @@ class ProgramBuilder {
     String name = namer.getNameOfClass(element);
     String holderName = namer.globalObjectFor(element);
     Holder holder = _registry.registerHolder(holderName);
-    Class result = new Class(name, holder, methods, fields);
+    bool onlyForRti =
+        _task.typeTestEmitter.rtiNeededClasses.contains(element);

[sigurdm, 2014/11/25 15:01:43]

Add a comment on `rtiNeededClasses` that it is the classes "only" needed for
rti. Or rename it to `classesOnleNeededForRti` or similar.

+    Class result = new Class(name, holder, methods, fields,
+                             onlyForRti: onlyForRti);
     _classes[element] = result;
     return result;
   }