Introduce a SchedulerHelper in content/child/scheduler

content/child/scheduler/null_idle_task_runner.cc

 // Copyright 2014 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.
 
-#include "content/browser/indexed_db/mock_indexed_db_factory.h"
+#include "content/child/scheduler/null_idle_task_runner.h"
 
 namespace content {
 
-MockIndexedDBFactory::MockIndexedDBFactory() {
+NullIdleTaskRunner::NullIdleTaskRunner()
+    : SingleThreadIdleTaskRunner(nullptr,
+                                 nullptr,
+                                 base::Callback<void(base::TimeTicks*)>(),
+                                 "null.taskrunner") {
 }
 
-MockIndexedDBFactory::~MockIndexedDBFactory() {
+NullIdleTaskRunner::~NullIdleTaskRunner() {
 }
 
-IndexedDBFactory::OriginDBs MockIndexedDBFactory::GetOpenDatabasesForOrigin(
-    const GURL& origin_url) const {
-  return OriginDBs();
+void NullIdleTaskRunner::PostIdleTask(
+    const tracked_objects::Location& from_here,
+    const IdleTask& idle_task) {
 }
 
 }  // namespace content