Introduce a new framework for back-and-forth tracked/protected preferences migration.

chrome/browser/prefs/chrome_pref_service_factory.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/chrome_pref_service_factory.h"
 
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 140 matching lines @@
   {
     13, prefs::kProfileResetPromptMemento,
     PrefHashFilter::ENFORCE_ON_LOAD,
     PrefHashFilter::TRACKING_STRATEGY_ATOMIC
   },
   {
     14, DefaultSearchManager::kDefaultSearchProviderDataPrefName,
     PrefHashFilter::NO_ENFORCEMENT,
     PrefHashFilter::TRACKING_STRATEGY_ATOMIC
   },
+  {
+    // Protecting kPreferenceResetTime does two things:
+    //  1) It ensures this isn't accidently set by someone stomping the pref
+    //     file.
+    //  2) More importantly, it declares kPreferenceResetTime as a protected
+    //     pref which is required for it to be visible when queried via the
+    //     SegregatedPrefStore. This is because it's written directly in the
+    //     protected JsonPrefStore by that store's PrefHashFilter if there was
+    //     a reset in FilterOnLoad and SegregatedPrefStore will not look for it
+    //     in the protected JsonPrefStore unless it's declared as a protected
+    //     preference here.
+    15, prefs::kPreferenceResetTime,
+    PrefHashFilter::ENFORCE_ON_LOAD,
+    PrefHashFilter::TRACKING_STRATEGY_ATOMIC
+  },
 };
 
 // The count of tracked preferences IDs across all platforms.
-const size_t kTrackedPrefsReportingIDsCount = 15;
+const size_t kTrackedPrefsReportingIDsCount = 16;
 COMPILE_ASSERT(kTrackedPrefsReportingIDsCount >= arraysize(kTrackedPrefs),
                need_to_increment_ids_count);
 
 // Each group enforces a superset of the protection provided by the previous
 // one.
 enum SettingsEnforcementGroup {
   GROUP_NO_ENFORCEMENT,
   // Only enforce settings on profile loads; still allow seeding of unloaded
   // profiles.
   GROUP_ENFORCE_ON_LOAD,
@@ skipping 341 matching lines @@
 
 void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry) {
   ProfilePrefStoreManager::RegisterProfilePrefs(registry);
 }
 
 void RegisterPrefs(PrefRegistrySimple* registry) {
   ProfilePrefStoreManager::RegisterPrefs(registry);
 }
 
 }  // namespace chrome_prefs