Revamp the MigrateBrowserPrefs and MigrateUserPrefs code.

chrome/browser/prefs/browser_prefs.cc

Index: chrome/browser/prefs/browser_prefs.cc
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index 88209877b10658772773b51080be1881dd9f9620..da97658fea8d4898a059a0cd5efb71cbb6c70f3d 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -230,7 +230,7 @@ enum MigratedPreferences {
 // chrome/browser/protector/protected_prefs_watcher.cc in source
 // control history) used this string as a prefix for various prefs it
 // registered. We keep it here for now to clear out those old prefs in
-// MigrateUserPrefs.
+// MigrateObsoleteProfilePrefs.
 const char kBackupPref[] = "backup";
 
 #if !defined(OS_ANDROID)
@@ -247,8 +247,6 @@ const char kLegacyProfileResetPromptMemento[] = "profile.reset_prompt_memento";
 namespace chrome {
 
 void RegisterLocalState(PrefRegistrySimple* registry) {
-  // Prefs in Local State.
-  registry->RegisterIntegerPref(prefs::kMultipleProfilePrefMigration, 0);
 
   // Please keep this list alphabetized.
   AppListService::RegisterPrefs(registry);
@@ -555,76 +553,40 @@ void RegisterLoginProfilePrefs(user_prefs::PrefRegistrySyncable* registry) {
 }
 #endif
 
-void MigrateUserPrefs(Profile* profile) {
-  PrefService* prefs = profile->GetPrefs();
+void MigrateObsoleteProfilePrefs(PrefService* profile_prefs) {
+  // This method should prune away migrations year+ old.
+
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+  // Added 06/2014.
+  autofill::AutofillManager::MigrateUserPrefs(profile_prefs);
+#endif  // defined(OS_MACOSX) && !defined(OS_IOS)
 
-  // Cleanup prefs from now-removed protector feature.
-  prefs->ClearPref(kBackupPref);
+  // Added 07/2014.
+  translate::TranslatePrefs::MigrateUserPrefs(profile_prefs,
+                                              prefs::kAcceptLanguages);
 
 #if !defined(OS_ANDROID)
+  // Added 08/2014.
   // Migrate kNetworkPredictionEnabled to kNetworkPredictionOptions when not on
   // Android.  On Android, platform-specific code performs preference migration.
   // TODO(bnc): https://crbug.com/401970  Remove migration code one year after
   // M38.
-  chrome_browser_net::MigrateNetworkPredictionUserPrefs(prefs);
+  chrome_browser_net::MigrateNetworkPredictionUserPrefs(profile_prefs);
 #endif
-
-  PromoResourceService::MigrateUserPrefs(prefs);
-  translate::TranslatePrefs::MigrateUserPrefs(prefs, prefs::kAcceptLanguages);
-
-#if defined(OS_MACOSX) && !defined(OS_IOS)
-  autofill::AutofillManager::MigrateUserPrefs(prefs);
-#endif  // defined(OS_MACOSX) && !defined(OS_IOS)
 }
 
-void MigrateBrowserPrefs(Profile* profile, PrefService* local_state) {
-  // Copy pref values which have been migrated to user_prefs from local_state,
-  // or remove them from local_state outright, if copying is not required.
-  int current_version =
-      local_state->GetInteger(prefs::kMultipleProfilePrefMigration);
-  PrefRegistrySimple* registry = static_cast<PrefRegistrySimple*>(
-      local_state->DeprecatedGetPrefRegistry());
-
-  if (!(current_version & DNS_PREFS)) {
-    registry->RegisterListPref(prefs::kDnsStartupPrefetchList);
-    local_state->ClearPref(prefs::kDnsStartupPrefetchList);
-
-    registry->RegisterListPref(prefs::kDnsHostReferralList);
-    local_state->ClearPref(prefs::kDnsHostReferralList);
+void MigrateObsoleteBrowserPrefs(PrefService* local_state) {
+  // This method should prune away migrations year+ old.
 
-    current_version |= DNS_PREFS;
-    local_state->SetInteger(prefs::kMultipleProfilePrefMigration,
-                            current_version);
-  }
-
-  PrefService* user_prefs = profile->GetPrefs();
-  if (!(current_version & WINDOWS_PREFS)) {
-    registry->RegisterDictionaryPref(prefs::kBrowserWindowPlacement);
-    if (local_state->HasPrefPath(prefs::kBrowserWindowPlacement)) {
-      const PrefService::Preference* pref =
-          local_state->FindPreference(prefs::kBrowserWindowPlacement);
-      DCHECK(pref);
-      user_prefs->Set(prefs::kBrowserWindowPlacement,
-                      *(pref->GetValue()));
-    }
-    local_state->ClearPref(prefs::kBrowserWindowPlacement);
-
-    current_version |= WINDOWS_PREFS;
-    local_state->SetInteger(prefs::kMultipleProfilePrefMigration,
-                            current_version);
-  }
+  // Added 05/2014.
+#if defined(TOOLKIT_VIEWS)
+  MigrateBrowserTabStripPrefs(local_state);
+#endif
 
+  // Added 08/2014.
 #if !defined(OS_ANDROID)
   local_state->ClearPref(kLegacyProfileResetPromptMemento);
 #endif
-
-#if defined(OS_CHROMEOS)
-  chromeos::default_pinned_apps_field_trial::MigratePrefs(local_state);
-#endif
-
-#if defined(TOOLKIT_VIEWS)
-  MigrateBrowserTabStripPrefs(local_state);
-#endif
 }
 
 // As part of the migration from per-profile to per-partition HostZoomMaps,