Fix "conversion of size_t to unsigned int" warning

net/dns/record_rdata.h

 // 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.
 
 #ifndef NET_DNS_RECORD_RDATA_H_
 #define NET_DNS_RECORD_RDATA_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/compiler_specific.h"
+#include "base/logging.h"
 #include "base/macros.h"
 #include "base/strings/string_piece.h"
 #include "net/base/ip_address.h"
 #include "net/base/net_export.h"
 #include "net/dns/dns_protocol.h"
 
 namespace net {
 
 class DnsRecordParser;
 
@@ skipping 166 matching lines @@
  public:
   static const uint16_t kType = dns_protocol::kTypeNSEC;
 
   ~NsecRecordRdata() override;
   static std::unique_ptr<NsecRecordRdata> Create(const base::StringPiece& data,
                                                  const DnsRecordParser& parser);
   bool IsEqual(const RecordRdata* other) const override;
   uint16_t Type() const override;
 
   // Length of the bitmap in bits.
-  unsigned bitmap_length() const { return bitmap_.size() * 8; }
+  // This will be between 8 and 256, per RFC 3845, Section 2.1.2.
+  uint16_t bitmap_length() const {
+    DCHECK_LE(bitmap_.size(), 32u);
+    return static_cast<uint16_t>(bitmap_.size() * 8);
+  }
 
   // Returns bit i-th bit in the bitmap, where bits withing a byte are organized
   // most to least significant. If it is set, a record with rrtype i exists for
   // the domain name of this nsec record.
   bool GetBit(unsigned i) const;
 
  private:
   NsecRecordRdata();
 
   std::vector<uint8_t> bitmap_;
 
   DISALLOW_COPY_AND_ASSIGN(NsecRecordRdata);
 };
 
 
 }  // namespace net
 
 #endif  // NET_DNS_RECORD_RDATA_H_