message: Remove the alpha annotation from AesCmac.
  I will add this to Tink, including cross language tests and performance testing. I think we can remove Alpha then.
diff: package com.google.crypto.tink.subtle;
  import com.google.crypto.tink.Mac;
  -import com.google.crypto.tink.annotations.Alpha;
  import java.security.GeneralSecurityException;
  import java.security.InvalidAlgorithmParameterException;
  import java.util.Arrays;
  @@ -27,14 +26,7 @@ import javax.crypto.spec.SecretKeySpec;
  /**
  * An implementation of CMAC following <a href="https://tools.ietf.org/html/rfc4493">RFC 4493</a>.
  - *
  - * <h3>Warning</h3>
  - *
  - * <p>Do not use this API or any other APIs including fields and methods marked with the @Alpha
  - * annotation. They can be modified in any way, or even removed, at any time. They are in the
  - * package, but not for official, production release, but only for testing.
  */
  -@Alpha
  public final class AesCmac implements Mac {
  static final int MIN_TAG_SIZE_IN_BYTES = 10;
  