Time Zone data loader

- Use CountryZonesFinder to provide time zone id and region-to-timezone
  mapping, where the underlying data is updatable through an unbundled time zone
  data app in some devices.

Bug: 73952488
Bug: 72144448
Test: m RunSettingsRoboTests
Change-Id: I2e01e167c48987ebb98d4881a1a528d16dd82944

src/com/android/settings/datetime/timezone/model/TimeZoneDataLoader.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2018 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.datetime.timezone.model;
+
+import android.app.LoaderManager;
+import android.content.Context;
+import android.content.Loader;
+import android.os.Bundle;
+
+import com.android.settingslib.utils.AsyncLoader;
+
+public class TimeZoneDataLoader extends AsyncLoader<TimeZoneData> {
+
+    public TimeZoneDataLoader(Context context) {
+        super(context);
+    }
+
+    @Override
+    public TimeZoneData loadInBackground() {
+        // Heavy operation due to reading the underlying file
+        return new TimeZoneData();
+    }
+
+    @Override
+    protected void onDiscardResult(TimeZoneData result) {
+        // This class doesn't hold resource of the result.
+    }
+
+    public interface OnDataReadyCallback {
+        void onTimeZoneDataReady(TimeZoneData data);
+    }
+
+    public static class LoaderCreator implements LoaderManager.LoaderCallbacks<TimeZoneData> {
+
+        private final Context mContext;
+        private final OnDataReadyCallback mCallback;
+
+        public LoaderCreator(Context context, OnDataReadyCallback callback) {
+            mContext = context;
+            mCallback = callback;
+        }
+
+        @Override
+        public Loader onCreateLoader(int id, Bundle args) {
+            return new TimeZoneDataLoader(mContext);
+        }
+
+        @Override
+        public void onLoadFinished(Loader<TimeZoneData> loader, TimeZoneData data) {
+            if (mCallback != null) {
+                mCallback.onTimeZoneDataReady(data);
+            }
+        }
+
+        @Override
+        public void onLoaderReset(Loader<TimeZoneData> loader) {
+            //It's okay to keep the time zone data when loader is reset
+        }
+    }
+}