Fix the toggle button flicker problem when display

- Root cause: the side effect of the parallel controller loading.
- Solution: disable the parallel approach and remove the entry point
  of parallel approach in DashboardFragment.

Fixes: 187838753
Test: Robo test for AppInfoDashboardFragment, ConfigureNotificationSettings,
      ConnectedDeviceDashboardFragment, DevelopmentSettingsDashboardFragment,
      NetworkDashboardFragment, DashboardFragment
Change-Id: If3b09c4fd6f33042e0ed38704f08e855ab8f5377

src/com/android/settings/dashboard/DashboardFragment.java

@@ -22,7 +22,6 @@ import android.content.Context;
 import android.os.Bundle;
 import android.text.TextUtils;
 import android.util.ArrayMap;
-import android.util.FeatureFlagUtils;
 import android.util.Log;
 
 import androidx.annotation.CallSuper;
@@ -36,7 +35,6 @@ import androidx.preference.SwitchPreference;
 import com.android.settings.R;
 import com.android.settings.SettingsPreferenceFragment;
 import com.android.settings.core.BasePreferenceController;
-import com.android.settings.core.FeatureFlags;
 import com.android.settings.core.PreferenceControllerListHelper;
 import com.android.settings.core.SettingsBaseActivity;
 import com.android.settings.overlay.FeatureFactory;
@@ -360,11 +358,6 @@ public abstract class DashboardFragment extends SettingsPreferenceFragment
      * Update state of each preference managed by PreferenceController.
      */
     protected void updatePreferenceStates() {
-        if (isParalleledControllers() && FeatureFlagUtils.isEnabled(getContext(),
-                FeatureFlags.CONTROLLER_ENHANCEMENT)) {
-            updatePreferenceStatesInParallel();
-            return;
-        }
         final PreferenceScreen screen = getPreferenceScreen();
         Collection<List<AbstractPreferenceController>> controllerLists =
                 mPreferenceControllers.values();
@@ -396,6 +389,8 @@ public abstract class DashboardFragment extends SettingsPreferenceFragment
      * Use parallel method to update state of each preference managed by PreferenceController.
      */
     @VisibleForTesting
+    // To use this parallel approach will cause the side effect of the UI flicker. Such as
+    // the thumb sliding of the toggle button.
     void updatePreferenceStatesInParallel() {
         final PreferenceScreen screen = getPreferenceScreen();
         final Collection<List<AbstractPreferenceController>> controllerLists =