Add help url placeholders for new pages

Bug: 38412798
Test: visual
Change-Id: I4ede523cb13790ea05309279f80a778b2086f850

src/com/android/settings/security/LockscreenDashboardFragment.java

@@ -67,6 +67,11 @@ public class LockscreenDashboardFragment extends DashboardFragment
         return R.xml.security_lockscreen_settings;
     }
 
+    @Override
+    protected int getHelpResource() {
+        return R.string.help_url_lockscreen;
+    }
+
     @Override
     protected List<PreferenceController> getPreferenceControllers(Context context) {
         final List<PreferenceController> controllers = new ArrayList<>();