[runtime] Introduce dedicated JSBoundFunction to represent bound functions.

src/snapshot/serialize.cc

Index: src/snapshot/serialize.cc
diff --git a/src/snapshot/serialize.cc b/src/snapshot/serialize.cc
index b729e60c6099add743de2b16e4232bf483cc9130..421cf0721cda7f2702da16e698986a94d9bde480 100644
--- a/src/snapshot/serialize.cc
+++ b/src/snapshot/serialize.cc
@@ -1796,7 +1796,7 @@ void PartialSerializer::SerializeObject(HeapObject* obj, HowToCode how_to_code,
   FlushSkip(skip);
 
   // Clear literal boilerplates.
-  if (obj->IsJSFunction() && !JSFunction::cast(obj)->shared()->bound()) {
+  if (obj->IsJSFunction()) {
     FixedArray* literals = JSFunction::cast(obj)->literals();
     for (int i = 0; i < literals->length(); i++) literals->set_undefined(i);
   }