[serializer] include global proxy in additional context snapshots.

test/cctest/test-lockers.cc

Index: test/cctest/test-lockers.cc
diff --git a/test/cctest/test-lockers.cc b/test/cctest/test-lockers.cc
index 4d4f3e2177bd789c569e266ee96d37c6264f4836..745d06f6ac943b4237ab2aff8c31553c46e6c41b 100644
--- a/test/cctest/test-lockers.cc
+++ b/test/cctest/test-lockers.cc
@@ -686,12 +686,9 @@ class IsolateGenesisThread : public JoinableThread {
     v8::Isolate* isolate = v8::Isolate::New(create_params);
     {
       v8::Isolate::Scope isolate_scope(isolate);
-      CHECK(
-          !reinterpret_cast<i::Isolate*>(isolate)->has_installed_extensions());
       v8::ExtensionConfiguration extensions(count_, extension_names_);
       v8::HandleScope handle_scope(isolate);
       v8::Context::New(isolate, &extensions);
-      CHECK(reinterpret_cast<i::Isolate*>(isolate)->has_installed_extensions());
     }
     isolate->Dispose();
   }