[webcrypto] Add JWK RSA public key export for NSS.

content/child/webcrypto/webcrypto_util.cc

Index: content/child/webcrypto/webcrypto_util.cc
diff --git a/content/child/webcrypto/webcrypto_util.cc b/content/child/webcrypto/webcrypto_util.cc
index d7326f990794a96d14d1712b89a6afeb3249e0eb..cbf8b3ddc8698a8c6847af08179b1947960e3955 100644
--- a/content/child/webcrypto/webcrypto_util.cc
+++ b/content/child/webcrypto/webcrypto_util.cc
@@ -67,6 +67,12 @@ std::string Base64EncodeUrlSafe(const base::StringPiece& input) {
   return output;
 }
 
+std::string Base64EncodeUrlSafe(const std::vector<uint8>& input) {
+  const base::StringPiece string_piece(
+      reinterpret_cast<const char*>(Uint8VectorStart(input)), input.size());
+  return Base64EncodeUrlSafe(string_piece);
+}
+
 struct JwkToWebCryptoUsage {
   const char* const jwk_key_op;
   const blink::WebCryptoKeyUsage webcrypto_usage;