Add TypeVariable object on runtime to support reflection on type variables.

sdk/lib/_internal/lib/js_rti.dart

Index: sdk/lib/_internal/lib/js_rti.dart
diff --git a/sdk/lib/_internal/lib/js_rti.dart b/sdk/lib/_internal/lib/js_rti.dart
index 432d2374021223ec4d8a611d91f38e4249691c72..e488a50269347e5b3c494da8f9912a2898ddc455 100644
--- a/sdk/lib/_internal/lib/js_rti.dart
+++ b/sdk/lib/_internal/lib/js_rti.dart
@@ -66,6 +66,20 @@ class TypeImpl implements Type {
   }
 }
 
+/**
+ * Represents a type variable.
+ *
+ * This class holds the information needed when reflecting on generic classes
+ * and their members.
+ */
+class TypeVariable {
+  final Type owner;
+  final String name;
+  final int bound;
+
+  const TypeVariable(this.owner, this.name, this.bound);
+}
+
 getMangledTypeName(TypeImpl type) => type._typeName;
 
 /**