Add help url placeholders for new pages

Bug: 38412798
Test: visual
Change-Id: I4ede523cb13790ea05309279f80a778b2086f850

src/com/android/settings/display/NightDisplaySettings.java

@@ -73,6 +73,11 @@ public class NightDisplaySettings extends SettingsPreferenceFragment
         mTemperaturePreference.setContinuousUpdates(true);
     }
 
+    @Override
+    protected int getHelpResource() {
+        return R.string.help_url_night_display;
+    }
+
     @Override
     public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
         super.onCreatePreferences(savedInstanceState, rootKey);