message: Add missing license boilerplate.
  ORIGINAL_AUTHOR=Thai Duong
  GitOrigin-RevId:
diff: +// Copyright 2017 Google Inc.
  +//
  +// Licensed under the Apache License, Version 2.0 (the "License");
  +// you may not use this file except in compliance with the License.
  +// You may obtain a copy of the License at
  +//
  +// http://www.apache.org/licenses/LICENSE-2.0
  +//
  +// Unless required by applicable law or agreed to in writing, software
  +// distributed under the License is distributed on an "AS IS" BASIS,
  +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  +// See the License for the specific language governing permissions and
  +// limitations under the License.
  +//
  +////////////////////////////////////////////////////////////////////////////////
  +
  package com.google.crypto.tink.subtle;
  import java.nio.ByteBuffer;
  