Replace NULL with nullptr or null in webrtc/base/.

webrtc/base/messagedigest.cc

 /*
  *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 16 matching lines @@
 const char DIGEST_SHA_256[] = "sha-256";
 const char DIGEST_SHA_384[] = "sha-384";
 const char DIGEST_SHA_512[] = "sha-512";
 
 static const size_t kBlockSize = 64;  // valid for SHA-256 and down
 
 MessageDigest* MessageDigestFactory::Create(const std::string& alg) {
   MessageDigest* digest = new OpenSSLDigest(alg);
   if (digest->Size() == 0) {  // invalid algorithm
     delete digest;
-    digest = NULL;
+    digest = nullptr;
   }
   return digest;
 }
 
 bool IsFips180DigestAlgorithm(const std::string& alg) {
   // These are the FIPS 180 algorithms.  According to RFC 4572 Section 5,
   // "Self-signed certificates (for which legacy certificates are not a
   // consideration) MUST use one of the FIPS 180 algorithms (SHA-1,
   // SHA-224, SHA-256, SHA-384, or SHA-512) as their signature algorithm,
   // and thus also MUST use it to calculate certificate fingerprints."
@@ skipping 110 matching lines @@
 }
 
 std::string ComputeHmac(const std::string& alg, const std::string& key,
                         const std::string& input) {
   std::string output;
   ComputeHmac(alg, key, input, &output);
   return output;
 }
 
 }  // namespace rtc