Revert of Pass per-frame task runners to Workers (when possible)

third_party/WebKit/Source/core/workers/ParentFrameTaskRunners.cpp

-// Copyright 2016 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 "core/workers/ParentFrameTaskRunners.h"
-
-#include "core/dom/Document.h"
-#include "core/dom/TaskRunnerHelper.h"
-#include "wtf/Assertions.h"
-
-namespace blink {
-
-ParentFrameTaskRunners::~ParentFrameTaskRunners()
-{
-}
-
-WebTaskRunner* ParentFrameTaskRunners::getUnthrottledTaskRunner()
-{
-    return m_unthrottledTaskRunner.get();
-}
-
-WebTaskRunner* ParentFrameTaskRunners::getTimerTaskRunner()
-{
-    return m_timerTaskRunner.get();
-}
-
-WebTaskRunner* ParentFrameTaskRunners::getLoadingTaskRunner()
-{
-    return m_loadingTaskRunner.get();
-}
-
-ParentFrameTaskRunners::ParentFrameTaskRunners(Document* document)
-    : m_unthrottledTaskRunner(TaskRunnerHelper::getUnthrottledTaskRunner(document)->clone())
-    , m_timerTaskRunner(TaskRunnerHelper::getTimerTaskRunner(document)->clone())
-    , m_loadingTaskRunner(TaskRunnerHelper::getLoadingTaskRunner(document)->clone())
-{
-    DCHECK(document->isContextThread());
-}
-
-} // namespace blink