Remove getCategoryKey() from DashboardFragment children.

Use the centralized registry to look up category key instead.

Bug: 32936784
Test: make RunSettingsRoboTests -j40
Change-Id: I0b8c72d70f93e4b5c58871ac90de41f69ad15653

src/com/android/settings/gestures/GestureSettings.java

@@ -121,11 +121,6 @@ public class GestureSettings extends DashboardFragment {
         }
     }
 
-    @Override
-    protected String getCategoryKey() {
-        return null;
-    }
-
     @Override
     protected String getLogTag() {
         return TAG;
@@ -170,7 +165,7 @@ public class GestureSettings extends DashboardFragment {
 
                     List<PreferenceController> preferenceControllers =
                             getPreferenceControllers(context);
-                    for(PreferenceController controller : preferenceControllers) {
+                    for (PreferenceController controller : preferenceControllers) {
                         controller.updateNonIndexableKeys(result);
                     }
                     return result;