Add Genericity enum in VM to distinguish how a type is uninstantiated.

runtime/vm/il_printer.cc

Index: runtime/vm/il_printer.cc
diff --git a/runtime/vm/il_printer.cc b/runtime/vm/il_printer.cc
index dd2c6ab3acdb57a500499b6dec8bae0655f0a6dd..dcfc067a11b5166cc11bef0d8c551b7d83ca67b0 100644
--- a/runtime/vm/il_printer.cc
+++ b/runtime/vm/il_printer.cc
@@ -636,14 +636,14 @@ void LoadFieldInstr::PrintOperandsTo(BufferFormatter* f) const {
 void InstantiateTypeInstr::PrintOperandsTo(BufferFormatter* f) const {
   const String& type_name = String::Handle(type().Name());
   f->Print("%s, ", type_name.ToCString());
-  instantiator()->PrintTo(f);
+  instantiator_type_arguments()->PrintTo(f);
 }
 
 
 void InstantiateTypeArgumentsInstr::PrintOperandsTo(BufferFormatter* f) const {
   const String& type_args = String::Handle(type_arguments().Name());
   f->Print("%s, ", type_args.ToCString());
-  instantiator()->PrintTo(f);
+  instantiator_type_arguments()->PrintTo(f);
 }