[webcrypto] Add JWK import of RSA public key for NSS.

content/renderer/webcrypto/webcrypto_util.cc

 // Copyright (c) 2013 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/renderer/webcrypto/webcrypto_util.h"
 
 #include "base/base64.h"
 #include "base/logging.h"
 #include "third_party/WebKit/public/platform/WebCryptoAlgorithm.h"
 #include "third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h"
@@ skipping 31 matching lines @@
   if (new_size == buffer->byteLength())
     return;
 
   blink::WebArrayBuffer new_buffer =
       blink::WebArrayBuffer::create(new_size, 1);
   DCHECK(!new_buffer.isNull());
   memcpy(new_buffer.data(), buffer->data(), new_size);
   *buffer = new_buffer;
 }
 
+// This function decodes unpadded 'base64url' encoded data, as described in
+// RFC4648 (http://www.ietf.org/rfc/rfc4648.txt) Section 5. To do this, first
+// change the incoming data to 'base64' encoding by applying the appropriate
+// transformation including adding padding if required, and then call a base64
+// decoder.
 bool Base64DecodeUrlSafe(const std::string& input, std::string* output) {
   std::string base64EncodedText(input);
   std::replace(base64EncodedText.begin(), base64EncodedText.end(), '-', '+');
   std::replace(base64EncodedText.begin(), base64EncodedText.end(), '_', '/');
   base64EncodedText.append((4 - base64EncodedText.size() % 4) % 4, '=');
   return base::Base64Decode(base64EncodedText, output);
 }
 
 blink::WebCryptoAlgorithm GetInnerHashAlgorithm(
     const blink::WebCryptoAlgorithm& algorithm) {
@@ skipping 103 matching lines @@
                                   key_length_bits);
 }
 
 blink::WebCryptoAlgorithm CreateAesGcmKeyGenAlgorithm(
     unsigned short key_length_bits) {
   return CreateAesKeyGenAlgorithm(blink::WebCryptoAlgorithmIdAesGcm,
                                   key_length_bits);
 }
 
 }  // namespace content