Make HandleCloserAgent walk in 4x multiples on x64

sandbox/win/src/handle_closer_test.cc

 // Copyright (c) 2011 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 "base/strings/stringprintf.h"
 #include "base/win/scoped_handle.h"
 #include "sandbox/win/src/handle_closer_agent.h"
 #include "sandbox/win/src/sandbox.h"
 #include "sandbox/win/src/sandbox_factory.h"
 #include "sandbox/win/src/target_services.h"
@@ skipping 55 matching lines @@
       // Create a unique marker file that is open while the test is running.
       // The handles leak, but it will be closed by the test or on exit.
       for (int i = 0; i < arraysize(kFileExtensions); ++i)
         EXPECT_NE(GetMarkerFile(kFileExtensions[i]), INVALID_HANDLE_VALUE);
       return SBOX_TEST_SUCCEEDED;
 
     case AFTER_REVERT: {
       // Brute force the handle table to find what we're looking for.
       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.
       HANDLE handle = NULL;
       int invalid_count = 0;
       base::string16 handle_name;
 
       if (!::GetProcessHandleCount(::GetCurrentProcess(), &handle_count))
         return SBOX_TEST_FAILED_TO_RUN_TEST;
 
       while (handle_count && invalid_count < kInvalidHandleThreshold) {
         reinterpret_cast<size_t&>(handle) += kHandleOffset;
         if (GetHandleName(handle, &handle_name)) {
@@ skipping 99 matching lines @@
   runner.SetTestState(AFTER_REVERT);
   sandbox::TargetPolicy* policy = runner.GetPolicy();
 
   // Sever the CSRSS connection by closing ALPC ports inside the sandbox.
   CHECK_EQ(policy->AddKernelObjectToClose(L"ALPC Port", NULL), SBOX_ALL_OK);
 
   EXPECT_EQ(SBOX_TEST_SUCCEEDED, runner.RunTest(L"RunThreadPool"));
 }
 
 }  // namespace sandbox