Introduce JSFunction::EnsureHasInitialMap method.

src/factory.h

Index: src/factory.h
diff --git a/src/factory.h b/src/factory.h
index 68980c521f384ed726f63d373223bc1d2fc606e8..e5b8ce6de4276d474a511f33351c3687f4619103 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -261,6 +261,8 @@ class Factory {
 
   Handle<JSObject> NewFunctionPrototype(Handle<JSFunction> function);
 
+  Handle<Map> NewInitialMap(Handle<JSFunction> function);
+
   Handle<Map> CopyWithPreallocatedFieldDescriptors(Handle<Map> map);
 
   // Copy the map adding more inobject properties if possible without
@@ -341,6 +343,8 @@ class Factory {
 
   void SetContent(Handle<JSArray> array, Handle<FixedArrayBase> elements);
 
+  Handle<JSGeneratorObject> NewJSGeneratorObject(Handle<JSFunction> function);
+
   Handle<JSArrayBuffer> NewJSArrayBuffer();
 
   Handle<JSTypedArray> NewJSTypedArray(ExternalArrayType type);