RenderThreadImpl::~RenderThreadImpl() {
  for (std::map<int, mojo::MessagePipeHandle>::iterator it =
           pending_render_frame_connects_.begin();
       it != pending_render_frame_connects_.end();
       ++it) {
    mojo::CloseRaw(it->second);
  }
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.