Update auto brightness pref summary to show on/off

Change-Id: I7914957cc9dbffcc12e34fc714bb9c37783a4f33
Fixes: 109885418
Test: robotests

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

@@ -21,6 +21,7 @@ import android.content.Context;
 import android.provider.Settings;
 import android.text.TextUtils;
 
+import com.android.settings.R;
 import com.android.settings.core.TogglePreferenceController;
 
 
@@ -59,4 +60,11 @@ public class AutoBrightnessPreferenceController extends TogglePreferenceControll
     public boolean isSliceable() {
         return TextUtils.equals(getPreferenceKey(), "auto_brightness");
     }
+
+    @Override
+    public CharSequence getSummary() {
+        return mContext.getText(isChecked()
+                ? R.string.auto_brightness_summary_on
+                : R.string.auto_brightness_summary_off);
+    }
 }