clang/win: Let some chromium_code targets build with -Wextra.

net/base/keygen_handler_win.cc

 // Copyright (c) 2011 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 "net/base/keygen_handler.h"
 
 #include <windows.h>
 #include <rpc.h>
 
 #include <list>
@@ skipping 165 matching lines @@
     if (key_container.key_id_.empty())
       return std::string();
 
     // Only create new key containers, so that existing key containers are not
     // overwritten.
     if (crypto::CryptAcquireContextLocked(key_container.provider_.receive(),
             key_container.key_id_.c_str(), NULL, PROV_RSA_FULL,
             CRYPT_SILENT | CRYPT_NEWKEYSET))
       break;
 
-    if (GetLastError() != NTE_BAD_KEYSET) {
+    if (GetLastError() != static_cast<DWORD>(NTE_BAD_KEYSET)) {
       LOG(ERROR) << "Keygen failed: Couldn't acquire a CryptoAPI provider "
                     "context: " << GetLastError();
       return std::string();
     }
   }
   if (attempt == kMaxAttempts) {
     LOG(ERROR) << "Keygen failed: Couldn't acquire a CryptoAPI provider "
                   "context: Max retries exceeded";
     return std::string();
   }
@@ skipping 16 matching lines @@
 
     std::string result;
     base::Base64Encode(spkac, &result);
 
     VLOG(1) << "Keygen succeeded";
     return result;
   }
 }
 
 }  // namespace net