CdmAdapter -> CdmPromiseAdapter -> CdmInitializedPromise -> CdmAdapter

// |cdm| ownership passed to the promise.
cdm->Initialize(std::make_unique<CdmInitializedPromise>(cdm_created_cb, cdm));

So if the initialization doesn't finish properly, e.g. the CDM never calls OnInitialized(), we'll leak the CdmAdapter and the CDM instance.