[Offline Pages] Add cached offline page utils and show usage in settings.

components/offline_pages/core/cached_offline_page_utils.h

+// 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.
+
+#ifndef COMPONENTS_OFFLINE_PAGES_CORE_CACHED_OFFLINE_PAGE_UTILS_H_
+#define COMPONENTS_OFFLINE_PAGES_CORE_CACHED_OFFLINE_PAGE_UTILS_H_
+
+#include "components/offline_pages/core/offline_page_types.h"
+
+namespace base {
+class Time;
+}
+
+namespace offline_pages {
+
+class OfflinePageModel;
+
+// A dedicated class of static methods used for all upper level cached offline
+// pages related utility functions. For example:
+//  Get total size of all cached offline pages.

[carlosk, 2017/05/03 18:13:52]

nit: add a bullet symbol to these lines like a "*" or "-". IMO the extra leading
space doesn't make it very clear.

[romax, 2017/05/03 19:46:21]

Done.

+//  Delete all cached offline pages.
+class CachedOfflinePageUtils {

[carlosk, 2017/05/03 18:13:52]

It seems to be more common in Chromium to use non-member static functions inside
a meaningful namespace instead of wrapping them into a class.
As this is already in the offline_pages namespace the CachedOfflinePageUtils
wrapper could be removed. Method names could need to be renamed but I think they
are clear enough even without the wrapping class.

[romax, 2017/05/03 19:46:21]

Done.

+ public:
+  // Get total size of cache offline pages for a given time range.
+  static void GetCachedOfflinePageSizeBetween(
+      OfflinePageModel* model,
+      const SizeCalculatedCallback& callback,
+      const base::Time& begin_time,
+      const base::Time& end_time);
+
+  // Get total size of cached offline pages.
+  static void GetCachedOfflinePageSize(OfflinePageModel* model,
+                                       const SizeCalculatedCallback& callback);
+
+  // Delete all cached offline pages.
+  static void DeleteCachedOfflinePage(OfflinePageModel* model,
+                                      const DeletePageCallback& callback);
+};
+
+}  // namespace offline_pages
+#endif  // COMPONENTS_OFFLINE_PAGES_CORE_CACHED_OFFLINE_PAGE_UTILS_H_