API: added function to find instance of template in prototype chain.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index c7f791cab4e685d1e7afd8edb5a0b5500c9ee393..a3bd3ce1ca6360626e6d2f4839eb552214238c05 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -100,6 +100,25 @@ PropertyDetails PropertyDetails::AsDeleted() {
   }
 
 
+bool Object::IsInstanceOf(FunctionTemplateInfo* expected) {
+  // There is a constraint on the object; check.
+  if (!this->IsJSObject()) return false;
+  // Fetch the constructor function of the object.
+  Object* cons_obj = JSObject::cast(this)->map()->constructor();
+  if (!cons_obj->IsJSFunction()) return false;
+  JSFunction* fun = JSFunction::cast(cons_obj);
+  // Iterate through the chain of inheriting function templates to
+  // see if the required one occurs.
+  for (Object* type = fun->shared()->function_data();
+       type->IsFunctionTemplateInfo();
+       type = FunctionTemplateInfo::cast(type)->parent_template()) {
+    if (type == expected) return true;
+  }
+  // Didn't find the required type in the inheritance chain.
+  return false;
+}
+
+
 bool Object::IsSmi() {
   return HAS_SMI_TAG(this);
 }