dart2js cps: 'is'-check directly against type variables.

pkg/compiler/lib/src/js_backend/codegen/glue.dart

Index: pkg/compiler/lib/src/js_backend/codegen/glue.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/glue.dart b/pkg/compiler/lib/src/js_backend/codegen/glue.dart
index cb87354e609e6cc853493ff01f70df3b8b687bbc..ae0544ca72dc7d6300ad000c71db18b9bc02e2b4 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/glue.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/glue.dart
@@ -171,10 +171,16 @@ class Glue {
     return _backend.getSetRuntimeTypeInfo();
   }
 
+  /// checkSubtype(value, $isT, typeArgs, $asT)
   FunctionElement getCheckSubtype() {
     return _backend.getCheckSubtype();
   }
 
+  /// checkSubtypeOfRuntime(value, runtimeType)
+  FunctionElement getCheckSubtypeOfRuntime() {
+    return _backend.getCheckSubtypeOfRuntimeType();
+  }
+
   js.Expression getRuntimeTypeName(ClassElement cls) {
     return js.string(_namer.runtimeTypeName(cls));
   }