win: Fix a few minor issues found by clang.

sandbox/src/sandbox_nt_util.cc

 // Copyright (c) 2006-2010 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/src/sandbox_nt_util.h"
 
 #include "base/win/pe_image.h"
 #include "sandbox/src/sandbox_factory.h"
 #include "sandbox/src/target_services.h"
 
@@ skipping 520 matching lines @@
 }
 
 }  // namespace sandbox
 
 void* operator new(size_t size, sandbox::AllocationType type,
                    void* near_to) {
   using namespace sandbox;
 
   if (NT_ALLOC == type) {
     if (!InitHeap())
-      return false;
+      return NULL;
 
     // Use default flags for the allocation.
     return g_nt.RtlAllocateHeap(sandbox::g_heap, 0, size);
   } else if (NT_PAGE == type) {
     return AllocateNearTo(near_to, size);
   }
   NOTREACHED_NT();
   return NULL;
 }
 
@@ skipping 25 matching lines @@
   UNREFERENCED_PARAMETER(type);
   return buffer;
 }
 
 void __cdecl operator delete(void* memory, void* buffer,
                              sandbox::AllocationType type) {
   UNREFERENCED_PARAMETER(memory);
   UNREFERENCED_PARAMETER(buffer);
   UNREFERENCED_PARAMETER(type);
 }