Wrap format tokens in placeholders.

This will keep them from accidentally getting corrupted in translation.

Bug 6015825

Change-Id: Id724d3e753ff1e123ada8b70d31fa8b9ae20ce64
diff --git a/res/values/strings.xml b/res/values/strings.xml
index fa67483..a88e6a8 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -873,7 +873,7 @@
     <string name="vcard_unknown_filename">contact</string>
 
     <!-- The percentage, used for expressing the progress of vCard import/export. -->
-    <string name="percentage">%s%%</string>
+    <string name="percentage"><xliff:g id="percentage" example="50">%s</xliff:g><xliff:g id="percentsign" example="%">%%</xliff:g></string>
 
     <!-- Dialog title shown when a user confirms whether he/she export Contact data. [CHAR LIMIT=32] -->
     <string name="confirm_export_title">Export contacts?</string>