[es6] Reintroduce the instanceof operator in the backends.

src/runtime/runtime-operators.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/arguments.h"
 #include "src/isolate-inl.h"
 #include "src/runtime/runtime-utils.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 198 matching lines @@
 RUNTIME_FUNCTION(Runtime_GreaterThanOrEqual) {
   HandleScope scope(isolate);
   DCHECK_EQ(2, args.length());
   CONVERT_ARG_HANDLE_CHECKED(Object, x, 0);
   CONVERT_ARG_HANDLE_CHECKED(Object, y, 1);
   Maybe<bool> result = Object::GreaterThanOrEqual(x, y);
   if (!result.IsJust()) return isolate->heap()->exception();
   return isolate->heap()->ToBoolean(result.FromJust());
 }
 
+RUNTIME_FUNCTION(Runtime_InstanceOf) {
+  HandleScope shs(isolate);
+  DCHECK_EQ(2, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
+  CONVERT_ARG_HANDLE_CHECKED(Object, callable, 1);
+  Handle<Object> result;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, result, Object::InstanceOf(isolate, object, callable));
+  return *result;
+}
+
 }  // namespace internal
 }  // namespace v8