[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 294c4b2264c0cd3aaa40284ea87cf0b9bd977d36..c466daf38fa5d67586027ba8ff6ca9954c5335f7 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;