[Offlining] Updates the tab helper to use the async OfflinePageModel API

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"
+
 class GURL;
 
 namespace content {
 class BrowserContext;
 }
 
 namespace offline_pages {
 struct OfflinePageItem;
 
 class OfflinePageUtils {
  public:
   // Returns true if |url| might point to an offline page.
   static bool MightBeOfflineURL(const GURL& url);
 
   // Gets an offline URL of an offline page with |online_url| if one exists.
-  static GURL GetOfflineURLForOnlineURL(
+  // Deprecated.  Use |GetOfflineURLForOnlineURL|.
+  static GURL MaybeGetOfflineURLForOnlineURL(
       content::BrowserContext* browser_context,
       const GURL& online_url);
 
+  static void GetOfflineURLForOnlineURL(
+      content::BrowserContext* browser_context,
+      const GURL& online_url,
+      const base::Callback<void(const GURL&)>& callback);
+
   // Gets an online URL of an offline page with |offline_url| if one exists.
-  static GURL GetOnlineURLForOfflineURL(
+  // Deprecated.  Use |GetOnlineURLForOfflineURL|.
+  static GURL MaybeGetOnlineURLForOfflineURL(
       content::BrowserContext* browser_context,
       const GURL& offline_url);
 
+  static void GetOnlineURLForOfflineURL(
+      content::BrowserContext* browser_context,
+      const GURL& offline_url,
+      const base::Callback<void(const GURL&)>& callback);
+
   // Checks whether |offline_url| points to an offline page.
+  // Deprecated.  Use something else.
   static bool IsOfflinePage(content::BrowserContext* browser_context,
                             const GURL& offline_url);
 
   // Checks whether offline page for |online_url| exists.
   static bool HasOfflinePageForOnlineURL(
       content::BrowserContext* browser_context,
       const GURL& online_url);
 
   // Marks that the offline page related to the |offline_url| has been accessed.
   static void MarkPageAccessed(content::BrowserContext* browser_context,
                                const GURL& offline_url);
 };
 
 }  // namespace offline_pages
 
 #endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_UTILS_H_