Convert app_launch_index and page_index from int to StringOrdinal.

chrome/browser/extensions/extension_service.h

Index: chrome/browser/extensions/extension_service.h
diff --git a/chrome/browser/extensions/extension_service.h b/chrome/browser/extensions/extension_service.h
index 006d6551efc5250066578e51f9ded3f8903e344f..81048c840767b5dd4edecf3d53835ab344f38d30 100644
--- a/chrome/browser/extensions/extension_service.h
+++ b/chrome/browser/extensions/extension_service.h
@@ -389,7 +389,9 @@ class ExtensionService
 
   // Called by the backend when an extension has been installed.
   void OnExtensionInstalled(
-      const Extension* extension, bool from_webstore, int page_index);
+      const Extension* extension,
+      bool from_webstore,
+      const StringOrdinal& page_ordinal);
 
   // Initializes the |extension|'s active permission set and disables the
   // extension if the privilege level has increased (e.g., due to an upgrade).