Remove year+ old migration support of "session.urls_to_restore_on_startup".

chrome/browser/prefs/pref_model_associator.cc

Index: chrome/browser/prefs/pref_model_associator.cc
diff --git a/chrome/browser/prefs/pref_model_associator.cc b/chrome/browser/prefs/pref_model_associator.cc
index 9dfe86daa07a384a9490a476ce9d18abedcb3eeb..036ca1cbec9d5909b9b67a7c9339c121c574cda5 100644
--- a/chrome/browser/prefs/pref_model_associator.cc
+++ b/chrome/browser/prefs/pref_model_associator.cc
@@ -58,21 +58,29 @@ const struct MigratedPreferences {
   const char* const old_name;
   const char* const new_name;
 } kMigratedPreferences[] = {
-  { prefs::kURLsToRestoreOnStartupOld, prefs::kURLsToRestoreOnStartup },
+  // arraysize macro does not supports empty arrays, so we use a sentinel
+  // value when there are no migrated preferences.
+  { NULL, NULL },

[gab, 2015/08/24 21:48:45]

+zea: Think we should keep this around or simply get rid of it? I know it was
tricky to add so perhaps it is indeed worth keeping around an an empty list for
now?

[Nicolas Zea, 2015/08/25 17:10:30]

I'd rather get rid of it personally. If someone does want to bring it back,
it'll be preserved in the git history (and we could always leave a comment
explaining that if a migration does happen, where it should be performed and
how).

[sdefresne, 2015/08/26 16:00:56]

Done.

 };
 
 std::string GetOldMigratedPreferenceName(const char* preference_name) {
   for (size_t i = 0; i < arraysize(kMigratedPreferences); ++i) {
-    if (!strcmp(kMigratedPreferences[i].new_name, preference_name))
+    if (kMigratedPreferences[i].new_name &&
+        !strcmp(kMigratedPreferences[i].new_name, preference_name)) {
+      DCHECK(kMigratedPreferences[i].old_name);
       return kMigratedPreferences[i].old_name;
+    }
   }
   return std::string();
 }
 
 std::string GetNewMigratedPreferenceName(const char* old_preference_name) {
   for (size_t i = 0; i < arraysize(kMigratedPreferences); ++i) {
-    if (!strcmp(kMigratedPreferences[i].old_name, old_preference_name))
+    if (kMigratedPreferences[i].old_name &&
+        !strcmp(kMigratedPreferences[i].old_name, old_preference_name)) {
+      DCHECK(kMigratedPreferences[i].new_name);
       return kMigratedPreferences[i].new_name;
+    }
   }
   return std::string();
 }
@@ -318,8 +326,7 @@ scoped_ptr<base::Value> PrefModelAssociator::MergePreference(
     const base::Value& server_value) {
   // This function special cases preferences individually, so don't attempt
   // to merge for all migrated values.
-  if (name == prefs::kURLsToRestoreOnStartup ||
-      name == prefs::kURLsToRestoreOnStartupOld) {
+  if (name == prefs::kURLsToRestoreOnStartup) {
     return make_scoped_ptr(MergeListValues(local_value, server_value));
   }