Add 'Adaptive connectivity' UI

'Adaptive connectivity' toggle button controls whether
network connection is automatically managed.

Bug: 162871294
Test: make RunSettingsRoboTests
      manual
      Switch the toggle button and reboot device, observe
      if the state is retained.
Change-Id: I4499a3639abab356e8faa6316bfa45541efd63ac

src/com/android/settings/network/AdaptiveConnectivityTogglePreferenceController.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.network;
+
+import android.content.Context;
+import android.provider.Settings;
+
+import androidx.preference.PreferenceScreen;
+
+import com.android.settings.core.TogglePreferenceController;
+
+/**
+ * {@link TogglePreferenceController} that controls whether Adaptive connectivity option is enabled.
+ */
+public class AdaptiveConnectivityTogglePreferenceController extends TogglePreferenceController {
+
+    public AdaptiveConnectivityTogglePreferenceController(Context context, String preferenceKey) {
+        super(context, preferenceKey);
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        super.displayPreference(screen);
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return AVAILABLE;
+    }
+
+    @Override
+    public boolean isChecked() {
+        return Settings.Secure.getInt(mContext.getContentResolver(),
+                Settings.Secure.ADAPTIVE_CONNECTIVITY_ENABLED, 1) == 1;
+    }
+
+    @Override
+    public boolean setChecked(boolean isChecked) {
+        Settings.Secure.putInt(mContext.getContentResolver(),
+                Settings.Secure.ADAPTIVE_CONNECTIVITY_ENABLED,
+                isChecked ? 1 : 0);
+        return true;
+    }
+}