storage::BlobStorageContext* GetBlobStorageContext(
    ChromeBlobStorageContext* blob_storage_context) {
  if (!blob_storage_context)
    return NULL;
  return blob_storage_context->context();
}

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.