[Offline pages] Creating BackgroundJobScheduler, which uses JobScheduler

chrome/android/java/src/org/chromium/chrome/browser/offlinepages/BackgroundSchedulerJobService.java

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.offlinepages;
+
+import android.annotation.TargetApi;
+import android.app.job.JobParameters;
+import android.app.job.JobService;
+import android.os.Build;
+
+/**
+ * The background scheduler job service for handling background request in 5.1+.
+ */
+@TargetApi(Build.VERSION_CODES.LOLLIPOP_MR1)
+public class BackgroundSchedulerJobService extends JobService {
+    @Override
+    public boolean onStartJob(JobParameters params) {
+        // TODO(fgorski): Implement and expose in metadata.
+        // Perhaps initialize application context.
+        // Perhaps ensure one job runs at a time only.
+        // Kick off background processing of downloads here.
+        // Processing will happen on a separate thread, and we'll inform OS when done.
+        return true;
+    }
+
+    @Override
+    public boolean onStopJob(JobParameters params) {
+        // TODO(fgorski): Implement and expose in metadata.
+        // Issue a cancel signal to request coordinator.
+        // This is where synchronization might be necessary.
+        // If we didn't stop ourselves, that likely means there is more work to do.
+        return true;
+    }
+}