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/wifi/WifiSettings.java

@@ -305,7 +305,7 @@ public class WifiSettings extends RestrictedSettingsFragment
     /**
      * @return new WifiEnabler or null (as overridden by WifiSettingsForSetupWizard)
      */
-    /* package */ WifiEnabler createWifiEnabler() {
+    private WifiEnabler createWifiEnabler() {
         final SettingsActivity activity = (SettingsActivity) getActivity();
         return new WifiEnabler(activity, activity.getSwitchBar(), mMetricsFeatureProvider);
     }