Refine battery settings layout

- Add loading text to progress bar to prevent UI flaky
 - Setup enable/disable state for battery saver switch
 - Remove battery saver page divider

Bug: 177964551
Bug: 177964753
Bug: 184626649
Test: make SettingsRoboTests, visually
Change-Id: I8e05c0c0f02710729e1f59eff23fb3f425770de9

src/com/android/settings/fuelgauge/BatteryHeaderPreferenceController.java

@@ -50,7 +50,6 @@ public class BatteryHeaderPreferenceController extends BasePreferenceController
         BatteryPreferenceController {
     @VisibleForTesting
     static final String KEY_BATTERY_HEADER = "battery_header";
-    private static final String ANNOTATION_URL = "url";
     private static final int BATTERY_MAX_LEVEL = 100;
 
     @VisibleForTesting
@@ -87,6 +86,9 @@ public class BatteryHeaderPreferenceController extends BasePreferenceController
     public void displayPreference(PreferenceScreen screen) {
         super.displayPreference(screen);
         mBatteryUsageProgressBarPref = screen.findPreference(getPreferenceKey());
+        //Set up loading text first to prevent layout flaky before info loaded.
+        mBatteryUsageProgressBarPref.setBottomSummary(
+                mContext.getString(R.string.settings_license_activity_loading));
 
         if (com.android.settings.Utils.isBatteryPresent(mContext)) {
             quickUpdateHeaderPreference();