Fix "value possibly truncated" warnings on MSVC, net/spdy/ edition.

net/spdy/spdy_frame_builder.h

 // Copyright (c) 2012 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_SPDY_SPDY_FRAME_BUILDER_H_
 #define NET_SPDY_SPDY_FRAME_BUILDER_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 88 matching lines @@
     value = htonl(value);
     return WriteBytes(reinterpret_cast<char*>(&value) + 1,
                       sizeof(value) - 1);
   }
   bool WriteUInt32(uint32 value) {
     value = htonl(value);
     return WriteBytes(&value, sizeof(value));
   }
   bool WriteUInt64(uint64 value) {
     uint32 upper = htonl(value >> 32);
-    uint32 lower = htonl(value);
+    uint32 lower = htonl(static_cast<uint32>(value));
     return (WriteBytes(&upper, sizeof(upper)) &&
             WriteBytes(&lower, sizeof(lower)));
   }
   // TODO(hkhalil) Rename to WriteStringPiece16().
   bool WriteString(const std::string& value);
   bool WriteStringPiece32(const base::StringPiece& value);
   bool WriteBytes(const void* data, uint32 data_len);
 
   // Update (in-place) the length field in the frame being built to reflect the
   // current actual length of bytes written to said frame through this builder.
@@ skipping 23 matching lines @@
   size_t capacity_;  // Allocation size of payload, set by constructor.
   size_t length_;    // Length of the latest frame in the buffer.
   size_t offset_;    // Position at which the latest frame begins.
 
   const SpdyMajorVersion version_;
 };
 
 }  // namespace net
 
 #endif  // NET_SPDY_SPDY_FRAME_BUILDER_H_