Make GetBestPageForOnlineURL async

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;
 class WebContents;
 }
 
 namespace offline_pages {
 struct OfflinePageItem;
 
 class OfflinePageUtils {
  public:
   // Returns true if |url| might point to an offline page.
   static bool MightBeOfflineURL(const GURL& url);
 
+  // Returns via callback an offline page saved for |online_url|, if any. The
+  // best page is chosen based on creation date; a more recently created offline
+  // page will be preferred over an older one.

[Dmitry Titov, 2016/08/10 02:56:37]

please add info to the comment on why tab_id is passed in.

Also, the naming is weird. "best" from which point of view? I think this is
selecting a page for automatic redirect to offline page, perhaps the name should
reflect that. Maybe GetOfflinePageForBrowserRedirect()?

[jianli, 2016/08/11 00:33:27]

Per discussion, renamed to SelectPageForOnlineURL. Also added comment for
tab_id.

+  static void GetBestPageForOnlineURL(
+      content::BrowserContext* browser_context,
+      const GURL& online_url,
+      int tab_id,
+      const base::Callback<void(const OfflinePageItem*)>& callback);
+
   // Gets an online URL of an offline page with |offline_url| if one exists.
   // 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);
@@ skipping 20 matching lines @@
 
   // Gets an Android Tab ID from a tab containing |web_contents|. Returns false,
   // when tab is not available. Returns true otherwise and sets |tab_id| to the
   // ID of the tab.
   static bool GetTabId(content::WebContents* web_contents, int* tab_id);
 };
 
 }  // namespace offline_pages
 
 #endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_UTILS_H_