Changed previews component to be a layered component.

components/previews/previews_ui_service.cc

-// 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 "components/previews/previews_ui_service.h"
-
-#include "components/previews/previews_io_data.h"
-
-namespace previews {
-
-PreviewsUIService::PreviewsUIService(
-    PreviewsIOData* previews_io_data,
-    const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner)
-    : io_task_runner_(io_task_runner), weak_factory_(this) {
-  previews_io_data->Initialize(weak_factory_.GetWeakPtr());
-}
-
-PreviewsUIService::~PreviewsUIService() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-}
-
-void PreviewsUIService::SetIOData(base::WeakPtr<PreviewsIOData> io_data) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  io_data_ = io_data;
-}
-
-}  // namespace previews