PreferenceControllers are the way of the future.

Migrates Notification settings (app level, group level, and channel
level) into PreferenceControllers (and most importantly:
PreferenceControllerTest)

Note: this removes the 'Advanced' preference group, but does
not yet use the standard system 'Advanced' grouping as it does
not currently support our use case (where we don't know how many
fields to show outside of 'Advanced' until onResume() and also
where we need fields to show below the 'Advanced' group).

Test: make RunSettingsRoboTests
Change-Id: Iddd1b4771922db322e5f73562e9d63ed077c5396

src/com/android/settings/notification/AppLinkPreferenceController.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2017 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.notification;
+
+import android.content.Context;
+import android.support.v7.preference.Preference;
+
+import com.android.settings.core.PreferenceControllerMixin;
+
+/**
+ * Controls link to reach more preference settings inside the app.
+ */
+public class AppLinkPreferenceController extends NotificationPreferenceController
+        implements PreferenceControllerMixin {
+
+    private static final String TAG = "AppLinkPrefContr";
+    private static final String KEY_APP_LINK = "app_link";
+
+    public AppLinkPreferenceController(Context context) {
+        super(context, null);
+    }
+
+    @Override
+    public String getPreferenceKey() {
+        return KEY_APP_LINK;
+    }
+
+    @Override
+    public boolean isAvailable() {
+        if (!super.isAvailable()) {
+            return false;
+        }
+        return mAppRow.settingsIntent != null;
+    }
+
+    public void updateState(Preference preference) {
+        if (mAppRow != null) {
+            preference.setIntent(mAppRow.settingsIntent);
+        }
+    }
+}