Add SSA instructions for reified type information

sdk/lib/_internal/js_runtime/lib/js_rti.dart

Index: sdk/lib/_internal/js_runtime/lib/js_rti.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/js_rti.dart b/sdk/lib/_internal/js_runtime/lib/js_rti.dart
index 65ae2576c9ee0b882bfd868eeb21c4371b3ebbf0..3ec79b8954b00709301dd46b2755bded6e17f0ef 100644
--- a/sdk/lib/_internal/js_runtime/lib/js_rti.dart
+++ b/sdk/lib/_internal/js_runtime/lib/js_rti.dart
@@ -134,10 +134,6 @@ getTypeArgumentByIndex(Object target, int index) {
   return rti == null ? null : getIndex(rti, index);
 }
 
-void copyTypeArguments(Object source, Object target) {
-  JS('var', r'#.$builtinTypeInfo = #.$builtinTypeInfo', target, source);
-}
-
 /**
  * Retrieves the class name from type information stored on the constructor
  * of [object].