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

content/child/webcrypto/shared_crypto_unittest.cc

Index: content/child/webcrypto/shared_crypto_unittest.cc
diff --git a/content/child/webcrypto/shared_crypto_unittest.cc b/content/child/webcrypto/shared_crypto_unittest.cc
index 6995b48c4b07868b63f7df252dc5f99df9611e5d..821945fb800bb70c7cb84b27d7ae94dc29c70568 100644
--- a/content/child/webcrypto/shared_crypto_unittest.cc
+++ b/content/child/webcrypto/shared_crypto_unittest.cc
@@ -810,7 +810,7 @@ TEST_F(SharedCryptoTest, AesCbcFailures) {
   // keys).
   EXPECT_STATUS(Status::ErrorUnexpectedKeyType(),
                 ExportKey(blink::WebCryptoKeyFormatSpki, key, &output));
-  EXPECT_STATUS(Status::ErrorUnsupported(),
+  EXPECT_STATUS(Status::ErrorUnexpectedKeyType(),
                 ExportKey(blink::WebCryptoKeyFormatPkcs8, key, &output));
 }
 
@@ -1681,7 +1681,7 @@ TEST_F(SharedCryptoTest, MAYBE(ImportExportSpki)) {
                 ExportKey(blink::WebCryptoKeyFormatSpki, key, &output));
 }
 
-TEST_F(SharedCryptoTest, MAYBE(ImportPkcs8)) {
+TEST_F(SharedCryptoTest, MAYBE(ImportExportPkcs8)) {
   // Passing case: Import a valid RSA key in PKCS#8 format.
   blink::WebCryptoKey key = blink::WebCryptoKey::createNull();
   ASSERT_STATUS_SUCCESS(ImportKey(
@@ -1704,6 +1704,11 @@ TEST_F(SharedCryptoTest, MAYBE(ImportPkcs8)) {
       "010001",
       CryptoData(key.algorithm().rsaHashedParams()->publicExponent()));
 
+  blink::WebArrayBuffer exported_key;
+  ASSERT_STATUS_SUCCESS(
+      ExportKey(blink::WebCryptoKeyFormatPkcs8, key, &exported_key));
+  ExpectArrayBufferMatchesHex(kPrivateKeyPkcs8DerHex, exported_key);
+
   // Failing case: Empty PKCS#8 data
   EXPECT_STATUS(Status::ErrorImportEmptyKeyData(),
                 ImportKey(blink::WebCryptoKeyFormatPkcs8,