Google remains the copyright holder of the submitted patch. There's nothing special in this from the project's perspective - in the absence of copyright assignm

Google remains the copyright holder of the submitted patch. There's nothing special in this from the project's perspective - in the absence of copyright assignment as a required part of patch submission, the default is that the submitter retains copyright. In this case, it's just Google claiming ownership of their employee's patch rather than the employee holding the copyright.