Relanding this as the earlier attempt caused a managed mode browser test to fail. That issue

chrome/browser/prefs/incognito_mode_prefs.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 "chrome/browser/prefs/incognito_mode_prefs.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 
+#if defined(OS_WIN)
+#include "base/win/metro.h"
+#endif  // OS_WIN
+
 // static
 bool IncognitoModePrefs::IntToAvailability(int in_value,
                                            Availability* out_value) {
   if (in_value < 0 || in_value >= AVAILABILITY_NUM_TYPES) {
     *out_value = ENABLED;
     return false;
   }
   *out_value = static_cast<Availability>(in_value);
   return true;
 }
 
 // static
 IncognitoModePrefs::Availability IncognitoModePrefs::GetAvailability(
     const PrefService* pref_service) {
   DCHECK(pref_service);
   int pref_value = pref_service->GetInteger(prefs::kIncognitoModeAvailability);
   Availability result = IncognitoModePrefs::ENABLED;
   bool valid = IntToAvailability(pref_value, &result);
   DCHECK(valid);
+#if defined(OS_WIN)
+  // Disable incognito mode windows if parental controls are on. This is only
+  // for Windows Vista and above.
+  if (base::win::IsParentalControlActivityLoggingOn()) {
+    if (result == IncognitoModePrefs::FORCED)
+      LOG(ERROR) << "Ignoring FORCED incognito. Parental control logging on";
+    return IncognitoModePrefs::DISABLED;
+  }
+#endif  // OS_WIN
   return result;
 }
 
 // static
 void IncognitoModePrefs::SetAvailability(PrefService* prefs,
                                          const Availability availability) {
   prefs->SetInteger(prefs::kIncognitoModeAvailability, availability);
 }
 
 // static
 void IncognitoModePrefs::RegisterUserPrefs(PrefService* pref_service) {
   DCHECK(pref_service);
   pref_service->RegisterIntegerPref(prefs::kIncognitoModeAvailability,
                                     IncognitoModePrefs::ENABLED,
                                     PrefService::UNSYNCABLE_PREF);
 }
 
 // static
 bool IncognitoModePrefs::ShouldLaunchIncognito(
     const CommandLine& command_line,
     const PrefService* prefs) {
   Availability incognito_avail = GetAvailability(prefs);
   return incognito_avail != IncognitoModePrefs::DISABLED &&
          (command_line.HasSwitch(switches::kIncognito) ||
           incognito_avail == IncognitoModePrefs::FORCED);
 }