Fixing remaining VC++ 2015 64-bit build breaks

sandbox/win/src/handle_inheritance_test.cc

 // 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.
 
 #include <stdio.h>
 
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/memory/shared_memory.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 64 matching lines @@
     return;
 
   base::SharedMemory test_shared_memory;
   ASSERT_TRUE(test_shared_memory.CreateAnonymous(1000));
   ASSERT_TRUE(test_shared_memory.Map(0));
 
   TestRunner runner;
   void* shared_handle = runner.GetPolicy()->AddHandleToShare(
       test_shared_memory.handle().GetHandle());
 
-  std::string command_line =
-      "HandleInheritanceTests_ValidInheritedHandle " +
-      base::UintToString(reinterpret_cast<unsigned int>(shared_handle));
+  std::string command_line = "HandleInheritanceTests_ValidInheritedHandle " +
+                             // Cast through uintptr_t and then unsigned int to
+                             // make the truncation explicit. Handles are size
+                             // of-pointer but are always 32-bit values.
+                             base::UintToString(static_cast<unsigned int>(
+                                 reinterpret_cast<uintptr_t>(shared_handle)));
   int result = runner.RunTest(base::UTF8ToUTF16(command_line).c_str());
   ASSERT_EQ(SBOX_TEST_SUCCEEDED, result);
 }
 
 }  // namespace sandbox