[api] add v8::Object::IsUndetectable

This will enable people to check if an object is
document.all without having to use tricks like
`typeof v === 'undefined' && v !== undefined`.

Change-Id: I74670e4d3886fcd90f0f3cef9c3644a24ee08fda
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2067681Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66412}

include/v8.h

@@ -4025,6 +4025,13 @@ class V8_EXPORT Object : public Value {
    */
   bool IsApiWrapper();
 
+  /**
+   * True if this object was created from an object template which was marked
+   * as undetectable. See v8::ObjectTemplate::MarkAsUndetectable for more
+   * information.
+   */
+  bool IsUndetectable();
+
   /**
    * Call an Object as a function if a callback is set by the
    * ObjectTemplate::SetCallAsFunctionHandler method.

src/api/api.cc

@@ -4859,6 +4859,11 @@ bool v8::Object::IsApiWrapper() {
   return self->IsApiWrapper();
 }
 
+bool v8::Object::IsUndetectable() {
+  auto self = i::Handle<i::JSObject>::cast(Utils::OpenHandle(this));
+  return self->IsUndetectable();
+}
+
 MaybeLocal<Value> Object::CallAsFunction(Local<Context> context,
                                          Local<Value> recv, int argc,
                                          Local<Value> argv[]) {

test/cctest/test-api.cc

@@ -6842,6 +6842,9 @@ THREADED_TEST(UndetectableObject) {
                               .ToLocalChecked()
                               ->NewInstance(env.local())
                               .ToLocalChecked();
+
+  CHECK(obj->IsUndetectable());
+
   CHECK(
       env->Global()->Set(env.local(), v8_str("undetectable"), obj).FromJust());