[Android] Implements OS upgrade check and rescheduling

components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskGcmTaskService.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 com.google.android.gms.gcm.GcmNetworkManager;
 import com.google.android.gms.gcm.GcmTaskService;
 import com.google.android.gms.gcm.TaskParams;
 
 import org.chromium.base.ContextUtils;
 import org.chromium.base.Log;
 import org.chromium.base.ThreadUtils;
 
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
@@ skipping 87 matching lines @@
                                           ContextUtils.getApplicationContext(), taskParams))) {
                 return GcmNetworkManager.RESULT_RESCHEDULE;
             }
         }
 
         return GcmNetworkManager.RESULT_SUCCESS;
     }
 
     @Override
     public void onInitializeTasks() {
+        // Ignore the event on OSs supporting JobScheduler.
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) return;
         BackgroundTaskSchedulerFactory.getScheduler().reschedule(
                 ContextUtils.getApplicationContext());
     }
 }