Convert app_launch_index and page_index from int to StringOrdinal.

chrome/common/string_ordinal.cc

Index: chrome/common/string_ordinal.cc
diff --git a/chrome/common/string_ordinal.cc b/chrome/common/string_ordinal.cc
index f07002639174353624db6cb6d9de3f82592720b1..09caa4476b2ff18ae6a7672b7f1c980d9d7452c8 100644
--- a/chrome/common/string_ordinal.cc
+++ b/chrome/common/string_ordinal.cc
@@ -174,6 +174,10 @@ StringOrdinal::StringOrdinal() : string_ordinal_(""),
                                  is_valid_(false) {
 }
 
+StringOrdinal StringOrdinal::CreateValidOrdinal() {
+  return StringOrdinal(std::string(1, kMidDigit));
+}
+
 bool StringOrdinal::IsValid() const {
   return is_valid_;
 }