Implement IsIndependent(Isolate*)

test/cctest/test-api.cc

Index: test/cctest/test-api.cc
diff --git a/test/cctest/test-api.cc b/test/cctest/test-api.cc
index 3be068009e275e53bb60903d812af6f841ab6069..425cc53aa770886804cef41f52bf07b8297ee8ac 100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -5315,11 +5315,14 @@ THREADED_TEST(IndependentWeakHandle) {
     object_a = v8::Persistent<v8::Object>::New(v8::Object::New());
   }
 
+  v8::Isolate* isolate = v8::Isolate::GetCurrent();
   bool object_a_disposed = false;
   object_a.MakeWeak(&object_a_disposed, &DisposeAndSetFlag);
   CHECK(!object_a.IsIndependent());
+  CHECK(!object_a.IsIndependent(isolate));
   object_a.MarkIndependent();
   CHECK(object_a.IsIndependent());
+  CHECK(object_a.IsIndependent(isolate));
   HEAP->PerformScavenge();
   CHECK(object_a_disposed);
 }