[Android] Native initialization task for BackgroundTaskScheduler

components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/TaskParameters.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.Context;
 import android.os.Bundle;
 import android.support.annotation.NonNull;
 
@@ skipping 19 matching lines @@
     }
 
     /**
      * @return the extras for this task.
      */
     @NonNull
     public Bundle getExtras() {
         return mExtras;
     }
 
-    static Builder create(int taskId) {
+    /** Creates a builder for task parameters. */
+    public static Builder create(int taskId) {
         return new Builder(taskId);
     }
 
-    static final class Builder {
+    /** Class for building a task parameters object. Public for testing */
+    public static final class Builder {
         private final int mTaskId;
         private Bundle mExtras;
 
         Builder(int taskId) {
             mTaskId = taskId;
         }
 
-        Builder addExtras(Bundle extras) {
+        public Builder addExtras(Bundle extras) {
             mExtras = extras;
             return this;
         }
 
-        TaskParameters build() {
+        public TaskParameters build() {
             return new TaskParameters(this);
         }
     }
 }