Generator objects have [[Class]] === "Generator"

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 5e2a2b18741507e4239bcfab8506712783a01c2c..01b885cafdb9d1b7ede7d9cf9d7289b707cee47c 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -1078,6 +1078,7 @@ void Factory::SetIdentityHash(Handle<JSObject> object, Smi* hash) {
 Handle<SharedFunctionInfo> Factory::NewSharedFunctionInfo(
     Handle<String> name,
     int number_of_literals,
+    bool is_generator,
     Handle<Code> code,
     Handle<ScopeInfo> scope_info) {
   Handle<SharedFunctionInfo> shared = NewSharedFunctionInfo(name);
@@ -1091,6 +1092,9 @@ Handle<SharedFunctionInfo> Factory::NewSharedFunctionInfo(
     literals_array_size += JSFunction::kLiteralsPrefixSize;
   }
   shared->set_num_literals(literals_array_size);
+  if (is_generator) {
+    shared->set_instance_class_name(isolate()->heap()->Generator_string());
+  }
   return shared;
 }