[Android] BackgroundTaskScheduler reschedule implementation

components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskSchedulerPrefs.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.content.SharedPreferences;
 
 import org.chromium.base.ContextUtils;
 
@@ skipping 56 matching lines @@
             String[] entryParts = entry.split(ENTRY_SEPARATOR);
             if (entryParts.length != 2 || entryParts[0] == null || entryParts[0].isEmpty()) {
                 continue;
             }
             scheduledTasksClassNames.add(entryParts[0]);
         }
 
         return scheduledTasksClassNames;
     }
 
+    /** Removes all scheduled tasks from shared preferences store. */
+    public static void removeAllTasks() {
+        ContextUtils.getAppSharedPreferences().edit().remove(KEY_SCHEDULED_TASKS).apply();
+    }
+
     private static void updateScheduledTasks(SharedPreferences prefs, Set<String> tasks) {
         SharedPreferences.Editor editor = prefs.edit();
         editor.putStringSet(KEY_SCHEDULED_TASKS, tasks);
         editor.apply();
     }
 
     /**
      * Converts a task info to a shared preference entry in the format:
      * BACKGROUND_TASK_CLASS_NAME:TASK_ID.
      * Task ID is necessary to be able to remove the entries from the shared preferences.
      */
     private static String toSharedPreferenceEntry(TaskInfo taskInfo) {
         return taskInfo.getBackgroundTaskClass().getName() + ENTRY_SEPARATOR + taskInfo.getTaskId();
     }
 }