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

content/child/webcrypto/shared_crypto.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/shared_crypto.h"
 
 #include "base/logging.h"
 #include "content/child/webcrypto/crypto_data.h"
 #include "content/child/webcrypto/platform_crypto.h"
 #include "content/child/webcrypto/webcrypto_util.h"
@@ skipping 589 matching lines @@
         return status;
       return platform::ExportKeyRaw(sym_key, buffer);
     }
     case blink::WebCryptoKeyFormatSpki: {
       platform::PublicKey* public_key;
       Status status = ToPlatformPublicKey(key, &public_key);
       if (status.IsError())
         return status;
       return platform::ExportKeySpki(public_key, buffer);
     }
+    case blink::WebCryptoKeyFormatPkcs8: {
+      platform::PrivateKey* private_key;
+      Status status = ToPlatformPrivateKey(key, &private_key);
+      if (status.IsError())
+        return status;
+      return platform::ExportKeyPkcs8(private_key, key.algorithm(), buffer);
+    }
     case blink::WebCryptoKeyFormatJwk:
       return ExportKeyJwk(key, buffer);
-    case blink::WebCryptoKeyFormatPkcs8:
-      // TODO(eroman):
-      return Status::ErrorUnsupported();
     default:
       return Status::ErrorUnsupported();
   }
 }
 
 Status ExportKey(blink::WebCryptoKeyFormat format,
                  const blink::WebCryptoKey& key,
                  blink::WebArrayBuffer* buffer) {
   if (!key.extractable())
     return Status::ErrorKeyNotExtractable();
@@ skipping 159 matching lines @@
                             key);
   if (status.IsError())
     return status;
 
   return ValidateDeserializedKey(*key, algorithm, type);
 }
 
 }  // namespace webcrypto
 
 }  // namespace content