Fixing remaining VC++ 2015 64-bit build breaks

content/public/common/common_param_traits.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.
 
 // This file is used to define IPC::ParamTraits<> specializations for a number
 // of types so that they can be serialized over IPC.  IPC::ParamTraits<>
 // specializations for basic types (like int and std::string) and types in the
 // 'base' project can be found in ipc/ipc_message_utils.h.  This file contains
 // specializations for types that are used by the content code, and which need
 // manual serialization code.  This is usually because they're not structs with
@@ skipping 64 matching lines @@
   static bool Read(const Message* m, base::PickleIterator* iter, param_type* p);
   static void Log(const param_type& p, std::string* l);
 };
 
 template <>
 struct ParamTraits<gfx::NativeWindow> {
   typedef gfx::NativeWindow param_type;
   static void Write(Message* m, const param_type& p) {
 #if defined(OS_WIN)
     // HWNDs are always 32 bits on Windows, even on 64 bit systems.
-    m->WriteUInt32(reinterpret_cast<uint32>(p));
+    // Cast through uintptr_t and then uint32 to make the truncation explicit.
+    m->WriteUInt32(static_cast<uint32>(reinterpret_cast<uintptr_t>(p)));
 #else
     m->WriteData(reinterpret_cast<const char*>(&p), sizeof(p));
 #endif
   }
   static bool Read(const Message* m, base::PickleIterator* iter,
                    param_type* r) {
 #if defined(OS_WIN)
     return iter->ReadUInt32(reinterpret_cast<uint32*>(r));
 #else
     const char *data;
     int data_size = 0;
     bool result = iter->ReadData(&data, &data_size);
     if (result && data_size == sizeof(gfx::NativeWindow)) {
       memcpy(r, data, sizeof(gfx::NativeWindow));
     } else {
       result = false;
       NOTREACHED();
     }
     return result;
 #endif
   }
   static void Log(const param_type& p, std::string* l) {
     l->append("<gfx::NativeWindow>");
   }
 };
 
 }  // namespace IPC
 
 #endif  // CONTENT_PUBLIC_COMMON_COMMON_PARAM_TRAITS_H_