[Android] BackgroundTaskScheduler reschedule implementation

components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskScheduler.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.components.background_task_scheduler;
 
 import android.annotation.TargetApi;
 import android.content.Context;
 import android.os.Build;
 import android.support.annotation.Nullable;
 
 import org.chromium.base.Log;
 import org.chromium.base.ThreadUtils;
 
 import java.lang.reflect.Constructor;
+import java.util.Set;
 
 /**
  * A BackgroundTaskScheduler which is used to schedule jobs that run in the background.
  * It is backed by system APIs ({@link android.app.job.JobScheduler}) on newer platforms
  * and by GCM ({@link com.google.android.gms.gcm.GcmNetworkManager}) on older platforms.
  *
  * To get an instance of this class, use {@link BackgroundTaskSchedulerFactory#getScheduler()}.
  */
 @TargetApi(Build.VERSION_CODES.LOLLIPOP)
 public class BackgroundTaskScheduler {
@@ skipping 42 matching lines @@
      * Schedules a background task. See {@link TaskInfo} for information on what types of tasks that
      * can be scheduled.
      *
      * @param context the current context.
      * @param taskInfo the information about the task to be scheduled.
      * @return true if the schedule operation succeeded, and false otherwise.
      * @see TaskInfo
      */
     public boolean schedule(Context context, TaskInfo taskInfo) {
         ThreadUtils.assertOnUiThread();
-        BackgroundTaskSchedulerPrefs.addScheduledTask(taskInfo);
-        return mSchedulerDelegate.schedule(context, taskInfo);
+        boolean success = mSchedulerDelegate.schedule(context, taskInfo);
+        if (success) {
+            BackgroundTaskSchedulerPrefs.addScheduledTask(taskInfo);
+        }
+        return success;
     }
 
     /**
      * Cancels the task specified by the task ID.
      *
      * @param context the current context.
      * @param taskId the ID of the task to cancel. See {@link TaskIds} for a list.
      */
     public void cancel(Context context, int taskId) {
         ThreadUtils.assertOnUiThread();
         BackgroundTaskSchedulerPrefs.removeScheduledTask(taskId);
         mSchedulerDelegate.cancel(context, taskId);
     }
+
+    public void reschedule(Context context) {
+        Set<String> scheduledTasksClassNames = BackgroundTaskSchedulerPrefs.getScheduledTasks();
+        BackgroundTaskSchedulerPrefs.removeAllTasks();
+        for (String className : scheduledTasksClassNames) {
+            BackgroundTask task = getBackgroundTaskFromClassName(className);
+            if (task == null) {
+                Log.w(TAG, "Cannot reschedule task for: " + className);
+                continue;
+            }
+
+            task.reschedule(context);
+        }
+    }
 }