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

chrome/browser/android/offline_pages/offline_page_utils.h

 // Copyright 2015 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 CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_UTILS_H_
 #define CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_UTILS_H_
 
 #include <stdint.h>
 
 #include "base/callback.h"
 #include "components/offline_pages/core/offline_page_model.h"
+#include "components/offline_pages/core/offline_page_types.h"
 #include "url/gurl.h"
 
+namespace base {
+class Time;
+}
+
 namespace content {
 class BrowserContext;
 class WebContents;
 }
 
 namespace offline_pages {
 struct OfflinePageHeader;
 struct OfflinePageItem;
 
 class OfflinePageUtils {
@@ skipping 83 matching lines @@
   // different from the one rendered in |web_contents|.
   static void ScheduleDownload(content::WebContents* web_contents,
                                const std::string& name_space,
                                const GURL& url,
                                DownloadUIActionFlags ui_action);
 
   // Determines if offline page download should be triggered based on MIME type
   // of download resource.
   static bool CanDownloadAsOfflinePage(const GURL& url,
                                        const std::string& contents_mime_type);
+
+  // Get total size of cache offline pages for a given time range. Returns false
+  // when an OfflinePageModel cannot be acquired using the |browser_context|, or
+  // the time range is invalid (|begin_time| > |end_time|). Also returning false
+  // means no callback should be expected.
+  static bool GetCachedOfflinePageSizeBetween(
+      content::BrowserContext* browser_context,
+      const SizeInBytesCallback& callback,
+      const base::Time& begin_time,
+      const base::Time& end_time);
 };
 
 }  // namespace offline_pages
 
 #endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_UTILS_H_