Merge "Clarify how to replace cert generated by Android Keystore." into nyc-dev

<p>Generating a new {@link java.security.PrivateKey} requires that

  you also specify the initial X.509 attributes that the self-signed

  certificate will have. You can replace the certificate at a later

  time with a certificate signed by a Certificate Authority.</p>

  certificate will have. You can use

  {@link java.security.KeyStore#setKeyEntry(String, java.security.Key, char[], java.security.cert.Certificate[]) KeyStore.setKeyEntry}

  to replace the certificate at a later time with a certificate signed

  by a Certificate Authority (CA).</p>

<p>To generate the key, use a {@link java.security.KeyPairGenerator}

  with {@link android.security.KeyPairGeneratorSpec}:</p>