[Sync] Don't require keystore migration time to be set in nigori node

sync/internal_api/sync_encryption_handler_impl.cc

Index: sync/internal_api/sync_encryption_handler_impl.cc
diff --git a/sync/internal_api/sync_encryption_handler_impl.cc b/sync/internal_api/sync_encryption_handler_impl.cc
index f83c3e1a282b13e0ac685a44b32da50e5a31e274..089d37fe00287d4109a6a8fec6f7357a5797ddf7 100644
--- a/sync/internal_api/sync_encryption_handler_impl.cc
+++ b/sync/internal_api/sync_encryption_handler_impl.cc
@@ -77,8 +77,6 @@ enum NigoriMigrationState {
 bool IsNigoriMigratedToKeystore(const sync_pb::NigoriSpecifics& nigori) {
   if (!nigori.has_passphrase_type())
     return false;
-  if (!nigori.has_keystore_migration_time())
-    return false;
   if (!nigori.keybag_is_frozen())
     return false;
   if (nigori.passphrase_type() ==
@@ -88,8 +86,6 @@ bool IsNigoriMigratedToKeystore(const sync_pb::NigoriSpecifics& nigori) {
           sync_pb::NigoriSpecifics::KEYSTORE_PASSPHRASE &&
       nigori.keystore_decryptor_token().blob().empty())
     return false;
-  if (!nigori.has_keystore_migration_time())
-    return false;
   return true;
 }
 
@@ -896,7 +892,6 @@ bool SyncEncryptionHandlerImpl::ApplyNigoriUpdateImpl(
   }
   bool is_nigori_migrated = IsNigoriMigratedToKeystore(nigori);
   if (is_nigori_migrated) {
-    DCHECK(nigori.has_keystore_migration_time());
     migration_time_ = ProtoTimeToTime(nigori.keystore_migration_time());

[pavely, 2015/07/21 18:08:46]

Do we use migration_time_ anywhere other than displaying it in about:sync?
With this change migration_time_ might be null.

[Nicolas Zea, 2015/07/21 19:41:26]

It's only in about:sync. And yeah, I'm okay with it being null there.

     PassphraseType nigori_passphrase_type =
         ProtoPassphraseTypeToEnum(nigori.passphrase_type());