suppress user/password dialog when re-enabling sync

chrome/browser/sync/sync_prefs.cc

Index: chrome/browser/sync/sync_prefs.cc
diff --git a/chrome/browser/sync/sync_prefs.cc b/chrome/browser/sync/sync_prefs.cc
index 14a05ea6e1475a5b82eeb42669eaa2ba550c9154..619d78342f96d906670366aff499aae47a10c7b7 100644
--- a/chrome/browser/sync/sync_prefs.cc
+++ b/chrome/browser/sync/sync_prefs.cc
@@ -173,10 +173,20 @@ std::string SyncPrefs::GetEncryptionBootstrapToken() const {
 
 void SyncPrefs::SetEncryptionBootstrapToken(const std::string& token) {
   DCHECK(non_thread_safe_.CalledOnValidThread());
-  CHECK(pref_service_);
   pref_service_->SetString(prefs::kSyncEncryptionBootstrapToken, token);
 }
 
+std::string SyncPrefs::GetSpareBootstrapToken() const {
+  DCHECK(non_thread_safe_.CalledOnValidThread());
+  return pref_service_ ?
+      pref_service_->GetString(prefs::kSyncSpareBootstrapToken) : "";
+}
+
+void SyncPrefs::SetSpareBootstrapToken(const std::string& token) {
+  DCHECK(non_thread_safe_.CalledOnValidThread());
+  pref_service_->SetString(prefs::kSyncSpareBootstrapToken, token);
+}
+
 sync_notifier::InvalidationVersionMap SyncPrefs::GetAllMaxVersions() const {
   DCHECK(non_thread_safe_.CalledOnValidThread());
   if (!pref_service_) {
@@ -398,6 +408,9 @@ void SyncPrefs::RegisterPreferences() {
   pref_service_->RegisterStringPref(prefs::kSyncEncryptionBootstrapToken,
                                     "",
                                     PrefService::UNSYNCABLE_PREF);
+  pref_service_->RegisterStringPref(prefs::kSyncSpareBootstrapToken,
+                                    "",
+                                    PrefService::UNSYNCABLE_PREF);
 
   // We will start prompting people about new data types after the launch of
   // SESSIONS - all previously launched data types are treated as if they are