Misc tweaks to Indexable usage and tests.

- Make SettingsPreferenceFragment implement Indexable directly
- Add existing fragments that are SettingsPrefFragment but not Indexable
  to grandfather list.
- Fix "font size" fragment so it shows up in search properly.
- Remove duplicates for "lock screen display", "Screen saver".

Bug: 70720645
Test: robotests
Change-Id: I44ce0cac0fdf5e882b315861bb4bebc45dbe01e6
diff --git a/src/com/android/settings/SettingsPreferenceFragment.java b/src/com/android/settings/SettingsPreferenceFragment.java
index 5a5db45..d0bfa55 100644
--- a/src/com/android/settings/SettingsPreferenceFragment.java
+++ b/src/com/android/settings/SettingsPreferenceFragment.java
@@ -37,6 +37,7 @@
 import com.android.settings.applications.LayoutPreference;
 import com.android.settings.core.InstrumentedPreferenceFragment;
 import com.android.settings.core.instrumentation.InstrumentedDialogFragment;
+import com.android.settings.search.Indexable;
 import com.android.settings.search.actionbar.SearchMenuController;
 import com.android.settings.support.actionbar.HelpMenuController;
 import com.android.settings.support.actionbar.HelpResourceProvider;
@@ -61,7 +62,7 @@
  * Base class for Settings fragments, with some helper functions and dialog management.
  */
 public abstract class SettingsPreferenceFragment extends InstrumentedPreferenceFragment
-        implements DialogCreatable, HelpResourceProvider {
+        implements DialogCreatable, HelpResourceProvider, Indexable {
 
     private static final String TAG = "SettingsPreference";