Currently, we have this in ChildProcessSecurityPolicyImpl::CanAccessDataForOrigin:

  if (state == security_state_.end()) {
    // TODO(nick): Returning true instead of false here is a temporary
    // workaround for  https://crbug.com/600441 
    return true;
  }

 https://crbug.com/600441  is now marked as fixed, but it's not clear whether there are other cases where this can lead to cookie kills.  We should investigate and try to remove this, as having no record of a process shouldn't lead to blindly allowing access to cookies, etc.