Add migration from old to new NTP Promo pref structure.

ios/chrome/browser/notification_promo.cc

Index: ios/chrome/browser/notification_promo.cc
diff --git a/ios/chrome/browser/notification_promo.cc b/ios/chrome/browser/notification_promo.cc
index 11119b2332611769418c8002d528b06b9ee67c5b..e5f5d34392d5f2842382bd291056d0ed2bbc4b51 100644
--- a/ios/chrome/browser/notification_promo.cc
+++ b/ios/chrome/browser/notification_promo.cc
@@ -25,6 +25,7 @@ const char kNTPPromoFinchExperiment[] = "IOSNTPPromotion";
 const char kPrefPromoObject[] = "ios.ntppromo";
 
 // Keys in the kPrefPromoObject dictionary; used only here.
+const char kPrefPromoID[] = "id";
 const char kPrefPromoFirstViewTime[] = "first_view_time";
 const char kPrefPromoViews[] = "views";
 const char kPrefPromoClosed[] = "closed";
@@ -135,14 +136,21 @@ void NotificationPromo::MigrateUserPrefs(PrefService* user_prefs) {
 }
 
 void NotificationPromo::WritePrefs() {
+  WritePrefs(promo_id_, first_view_time_, views_, closed_);
+}
+
+void NotificationPromo::WritePrefs(int promo_id,
+                                   double first_view_time,
+                                   int views,
+                                   bool closed) {
   base::DictionaryValue* ntp_promo = new base::DictionaryValue;
-  ntp_promo->SetDouble(kPrefPromoFirstViewTime, first_view_time_);
-  ntp_promo->SetInteger(kPrefPromoViews, views_);
-  ntp_promo->SetBoolean(kPrefPromoClosed, closed_);
+  ntp_promo->SetDouble(kPrefPromoFirstViewTime, first_view_time);
+  ntp_promo->SetInteger(kPrefPromoViews, views);
+  ntp_promo->SetBoolean(kPrefPromoClosed, closed);
 
   base::DictionaryValue promo_dict;
   promo_dict.MergeDictionary(local_state_->GetDictionary(kPrefPromoObject));
-  promo_dict.Set(base::IntToString(promo_id_), ntp_promo);
+  promo_dict.Set(base::IntToString(promo_id), ntp_promo);
   local_state_->Set(kPrefPromoObject, promo_dict);
   DVLOG(1) << "WritePrefs " << promo_dict;
 }
@@ -150,6 +158,10 @@ void NotificationPromo::WritePrefs() {
 void NotificationPromo::InitFromPrefs(PromoType promo_type) {
   promo_type_ = promo_type;
 
+  // Check if data is stored in the old prefs structure, and migrate it before
+  // reading from prefs.
+  MigrateOldPrefs();
+
   // If |promo_id_| is not set, do nothing.
   if (promo_id_ == -1)
     return;
@@ -169,6 +181,48 @@ void NotificationPromo::InitFromPrefs(PromoType promo_type) {
   ntp_promo->GetBoolean(kPrefPromoClosed, &closed_);
 }
 
+void NotificationPromo::MigrateOldPrefs() {
+  const base::DictionaryValue* promo_dict =
+      local_state_->GetDictionary(kPrefPromoObject);
+  if (!promo_dict)
+    return;
+
+  const base::ListValue* promo_list = NULL;
+  promo_dict->GetList("mobile_ntp_whats_new_promo", &promo_list);
+  if (!promo_list)
+    return;
+
+  const base::DictionaryValue* ntp_promo = NULL;
+  promo_list->GetDictionary(0, &ntp_promo);
+  if (!ntp_promo) {
+    // If the list is saved but there is no promo dictionary, clear prefs to
+    // delete the empty list.
+    NotificationPromo::MigrateUserPrefs(local_state_);
+    return;
+  }
+
+  int promo_id = -1;
+  ntp_promo->GetInteger(kPrefPromoID, &promo_id);
+  if (promo_id == -1) {
+    // If there is no promo id saved in prefs, then data is corrupt and the
+    // prefs can be discarded.
+    NotificationPromo::MigrateUserPrefs(local_state_);
+    return;
+  }
+
+  double first_view_time = 0;
+  ntp_promo->GetDouble(kPrefPromoFirstViewTime, &first_view_time);
+  int views = 0;
+  ntp_promo->GetInteger(kPrefPromoViews, &views);
+  bool closed = false;
+  ntp_promo->GetBoolean(kPrefPromoClosed, &closed);
+
+  // Clear prefs to discard the old structure before saving the data in the new
+  // structure.
+  NotificationPromo::MigrateUserPrefs(local_state_);
+  WritePrefs(promo_id, first_view_time, views, closed);
+}
+
 bool NotificationPromo::CanShow() const {
   return !closed_ && !promo_text_.empty() && !ExceedsMaxViews() &&
          !ExceedsMaxSeconds() &&