[webcrypto] Add PKCS#8 export for RSA private keys for NSS.

content/child/webcrypto/platform_crypto_openssl.cc

 // Copyright 2014 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 "content/child/webcrypto/platform_crypto.h"
 
 #include <vector>
 #include <openssl/aes.h>
 #include <openssl/evp.h>
 #include <openssl/hmac.h>
@@ skipping 368 matching lines @@
                       blink::WebCryptoKey* key) {
   // TODO(eroman): http://crbug.com/267888
   return Status::ErrorUnsupported();
 }
 
 Status ExportKeySpki(PublicKey* key, blink::WebArrayBuffer* buffer) {
   // TODO(eroman): http://crbug.com/267888
   return Status::ErrorUnsupported();
 }
 
+Status ExportKeyPkcs8(PrivateKey* key,
+                      const blink::WebCryptoKeyAlgorithm& key_algorithm,
+                      blink::WebArrayBuffer* buffer) {
+  // TODO(eroman): http://crbug.com/267888
+  return Status::ErrorUnsupported();
+}
+
 Status WrapSymKeyAesKw(SymKey* wrapping_key,
                        SymKey* key,
                        blink::WebArrayBuffer* buffer) {
   // TODO(eroman): http://crbug.com/267888
   return Status::ErrorUnsupported();
 }
 
 Status UnwrapSymKeyAesKw(const CryptoData& wrapped_key_data,
                          SymKey* wrapping_key,
                          const blink::WebCryptoAlgorithm& algorithm,
@@ skipping 26 matching lines @@
                          blink::WebCryptoKey* key) {
   // TODO(eroman): http://crbug.com/267888
   return Status::ErrorUnsupported();
 }
 
 }  // namespace platform
 
 }  // namespace webcrypto
 
 }  // namespace content