Revert of [es6] Introduce spec compliant IsConstructor.

src/runtime/runtime-function.cc

Index: src/runtime/runtime-function.cc
diff --git a/src/runtime/runtime-function.cc b/src/runtime/runtime-function.cc
index be92d59a64ea9ae8ba62999eb8f0c1796335d452..560016659d6a6cf9998f7b2fd088a365f5eb415e 100644
--- a/src/runtime/runtime-function.cc
+++ b/src/runtime/runtime-function.cc
@@ -159,7 +159,7 @@
 
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, fun, 0);
   CONVERT_ARG_HANDLE_CHECKED(Object, value, 1);
-  RUNTIME_ASSERT(fun->IsConstructor());
+  RUNTIME_ASSERT(fun->should_have_prototype());
   RETURN_FAILURE_ON_EXCEPTION(isolate,
                               Accessors::FunctionSetPrototype(fun, value));
   return args[0];  // return TOS
@@ -270,10 +270,30 @@
 
 
 RUNTIME_FUNCTION(Runtime_IsConstructor) {
-  SealHandleScope shs(isolate);
-  DCHECK_EQ(1, args.length());
-  CONVERT_ARG_CHECKED(Object, object, 0);
-  return isolate->heap()->ToBoolean(object->IsConstructor());
+  HandleScope handles(isolate);
+  RUNTIME_ASSERT(args.length() == 1);
+
+  CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
+
+  // TODO(caitp): implement this in a better/simpler way, allow inlining via TF
+  if (object->IsJSFunction()) {
+    Handle<JSFunction> func = Handle<JSFunction>::cast(object);
+    bool should_have_prototype = func->should_have_prototype();
+    if (func->shared()->bound()) {
+      Handle<FixedArray> bound_args =
+          Handle<FixedArray>(FixedArray::cast(func->function_bindings()));
+      Handle<Object> bound_function(
+          JSReceiver::cast(bound_args->get(JSFunction::kBoundFunctionIndex)),
+          isolate);
+      if (bound_function->IsJSFunction()) {
+        Handle<JSFunction> bound = Handle<JSFunction>::cast(bound_function);
+        DCHECK(!bound->shared()->bound());
+        should_have_prototype = bound->should_have_prototype();
+      }
+    }
+    return isolate->heap()->ToBoolean(should_have_prototype);
+  }
+  return isolate->heap()->false_value();
 }
 
 
@@ -417,10 +437,6 @@
     bound_function_map = Map::TransitionToPrototype(bound_function_map, proto,
                                                     REGULAR_PROTOTYPE);
   }
-  if (bound_function_map->is_constructor() != bindee->IsConstructor()) {
-    bound_function_map = Map::Copy(bound_function_map, "IsConstructor");
-    bound_function_map->set_is_constructor(bindee->IsConstructor());
-  }
   JSObject::MigrateToMap(bound_function, bound_function_map);
 
   Handle<String> length_string = isolate->factory()->length_string();