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

content/child/webcrypto/platform_crypto.h

 // 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.
 
 #ifndef CONTENT_CHILD_WEBCRYPTO_PLATFORM_CRYPTO_H_
 #define CONTENT_CHILD_WEBCRYPTO_PLATFORM_CRYPTO_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "third_party/WebKit/public/platform/WebArrayBuffer.h"
@@ skipping 159 matching lines @@
 
 // Preconditions:
 //  * |key| is non-null.
 Status ExportKeyRaw(SymKey* key, blink::WebArrayBuffer* buffer);
 
 // Preconditions:
 //  * |key| is non-null.
 Status ExportKeySpki(PublicKey* key, blink::WebArrayBuffer* buffer);
 
 // Preconditions:
+//  * |key| is non-null.
+Status ExportKeyPkcs8(PrivateKey* key,
+                      const blink::WebCryptoKeyAlgorithm& key_algorithm,
+                      blink::WebArrayBuffer* buffer);
+
+// Preconditions:
 //  * |wrapping_key| is non-null
 //  * |key| is non-null
 Status WrapSymKeyAesKw(SymKey* wrapping_key,
                        SymKey* key,
                        blink::WebArrayBuffer* buffer);
 
 // Unwraps (decrypts) |wrapped_key_data| using AES-KW and places the results in
 // a WebCryptoKey. Raw key data remains inside NSS. This function should be used
 // when the input |wrapped_key_data| is known to result in symmetric raw key
 // data after AES-KW decryption.
@@ skipping 38 matching lines @@
                          blink::WebCryptoKeyUsageMask usage_mask,
                          blink::WebCryptoKey* key);
 
 }  // namespace platform
 
 }  // namespace webcrypto
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_WEBCRYPTO_PLATFORM_CRYPTO_H_