[Offline pages] Updates to background scheduling to use BTS

components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskSchedulerFactory.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.os.Build;
 
 import org.chromium.base.ThreadUtils;
 import org.chromium.base.VisibleForTesting;
@@ skipping 19 matching lines @@
     public static BackgroundTaskScheduler getScheduler() {
         ThreadUtils.assertOnUiThread();
         if (sInstance == null) {
             sInstance =
                     new BackgroundTaskScheduler(getSchedulerDelegateForSdk(Build.VERSION.SDK_INT));
         }
         return sInstance;
     }
 
     @VisibleForTesting
-    static void setSchedulerForTesting(BackgroundTaskScheduler scheduler) {
+    public static void setSchedulerForTesting(BackgroundTaskScheduler scheduler) {
         sInstance = scheduler;
     }
 
     // Do not instantiate.
     private BackgroundTaskSchedulerFactory() {}
 }