Make HandleCloserAgent walk in 4x multiples on x64

sandbox/win/src/handle_closer_agent.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 "sandbox/win/src/handle_closer_agent.h"
 
 #include "base/logging.h"
 #include "sandbox/win/src/nt_internals.h"
 #include "sandbox/win/src/win_utils.h"
 
@@ skipping 60 matching lines @@
   }
 
   // Clean up the memory we copied over.
   ::VirtualFree(g_handles_to_close, 0, MEM_RELEASE);
   g_handles_to_close = NULL;
 }
 
 bool HandleCloserAgent::CloseHandles() {
   DWORD handle_count = UINT_MAX;
   const int kInvalidHandleThreshold = 100;
-  const size_t kHandleOffset = sizeof(HANDLE);
+  const size_t kHandleOffset = 4;  // Handles are always a multiple of 4.
 
   if (!::GetProcessHandleCount(::GetCurrentProcess(), &handle_count))
     return false;
 
   // Set up buffers for the type info and the name.
   std::vector<BYTE> type_info_buffer(sizeof(OBJECT_TYPE_INFORMATION) +
                                      32 * sizeof(wchar_t));
   OBJECT_TYPE_INFORMATION* type_info =
       reinterpret_cast<OBJECT_TYPE_INFORMATION*>(&(type_info_buffer[0]));
   base::string16 handle_name;
@@ skipping 44 matching lines @@
         return false;
       if (!::CloseHandle(handle))
         return false;
     }
   }
 
   return true;
 }
 
 }  // namespace sandbox