Reorganize spell checkers settings

Bug: 15976603
Bug: 16115751
Change-Id: I3b23d7f01d8d39da27215a5263b12304ac64db0f
diff --git a/res/xml/language_settings.xml b/res/xml/language_settings.xml
index 35926a0..b493a0f 100644
--- a/res/xml/language_settings.xml
+++ b/res/xml/language_settings.xml
@@ -25,10 +25,14 @@
             android:fragment="com.android.settings.LocalePicker"
             />
 
-    <com.android.settings.inputmethod.SpellCheckersPreference
+    <!-- Spell checker preference title, summary and fragment will be set programmatically. -->
+    <!-- Note: Mark this as persistent="false" to remove unnecessarily saved shared preference.
+         See: InputMethodAndSubtypeUtil.removeUnnecessaryNonPersistentPreference. -->
+    <PreferenceScreen
             android:key="spellcheckers_settings"
             android:title="@string/spellcheckers_settings_title"
             settings:keywords="@string/keywords_spell_checker"
+            android:persistent="false"
             />
 
     <!-- User dictionary preference title and fragment will be set programmatically. -->