static String getKeyType() {
    return "type.googleapis.com/google.crypto.tink.AesGcmHkdfStreamingKey";
  }
This key manager generates new {@code AesGcmHkdfStreamingKey} keys and produces new instances of
{@code AesGcmHkdfStreaming}.
java_src/src/main/java/com/google/crypto/tink/streamingaead/AesGcmHkdfStreamingKeyManager.java