Add ChaCha20Poly1305Encrypter, based on

net/quic/crypto/chacha20_poly1305_encrypter_nss.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/quic/crypto/chacha20_poly1305_encrypter.h"
+
+// This is a bodge to allow this code to be compiled against system NSS
+// headers.
+#if defined(USE_NSS)
+#define CKM_NSS_CHACHA20_POLY1305 (CKM_NSS + 26)
+#endif
+
+using base::StringPiece;
+
+namespace net {
+
+namespace {
+
+const size_t kKeySize = 32;
+const size_t kNoncePrefixSize = 0;
+
+}  // namespace
+
+ChaCha20Poly1305Encrypter::ChaCha20Poly1305Encrypter()
+    : AeadBaseEncrypter(CKM_NSS_CHACHA20_POLY1305, kKeySize, kAuthTagSize,
+                        kNoncePrefixSize) {
+  COMPILE_ASSERT(kKeySize <= kMaxKeySize, key_size_too_big);
+  COMPILE_ASSERT(kNoncePrefixSize <= kMaxNoncePrefixSize,
+                 nonce_prefix_size_too_big);
+}
+
+ChaCha20Poly1305Encrypter::~ChaCha20Poly1305Encrypter() {}
+
+// static
+bool ChaCha20Poly1305Encrypter::IsSupported() {
+#if defined(USE_NSS)
+  // System NSS doesn't support ChaCha20+Poly1305 yet.
+  return false;
+#else
+  // TODO(wtc): return true when FillAeadParams is implemented.
+  return false;
+#endif
+}
+
+void ChaCha20Poly1305Encrypter::FillAeadParams(StringPiece nonce,
+                                               StringPiece associated_data,
+                                               size_t auth_tag_size,
+                                               AeadParams* aead_params) const {
+  // TODO(wtc): implement this.
+}
+
+}  // namespace net