Make GetBestPageForOnlineURL async

chrome/browser/android/offline_pages/offline_page_tab_helper.h

 // 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.
 
 #ifndef CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_TAB_HELPER_H_
 #define CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_TAB_HELPER_H_
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
@@ skipping 14 matching lines @@
 class OfflinePageTabHelper :
     public content::WebContentsObserver,
     public content::WebContentsUserData<OfflinePageTabHelper> {
  public:
   // Delegate that is used to better handle external dependencies.
   // Default implementation is in .cc file, while tests provide an override.
   class Delegate {
    public:
     virtual ~Delegate() {}
     virtual bool GetTabId(content::WebContents* web_contents,
-                          std::string* tab_id) const = 0;
+                          int* tab_id) const = 0;
     virtual base::Time Now() const = 0;
   };
 
   // This enum is used for UMA reporting. It contains all possible outcomes of
   // redirect intent and result. Generally one of these outcomes will happen.
   // The fringe errors (like no OfflinePageModel, etc.) are not reported due
   // to their low probability.
   // NOTE: because this is used for UMA reporting, these values should not be
   // changed or reused; new values should be ended immediately before the MAX
   // value. Make sure to update the histogram enum
@@ skipping 41 matching lines @@
       content::NavigationHandle* navigation_handle) override;
 
   void RedirectToOnline(const GURL& from_url,
                         const OfflinePageItem* offline_page);
 
   // 3 step redirection to the offline page. First getting all the pages, then
   // selecting appropriate page to redirect to and finally attempting to
   // redirect to that offline page, and caching metadata of that page locally.
   // RedirectResult is accumulated along the codepath to reflect the overall
   // result of redirection - and be reported to UMA at the end.
-  void GetPagesForRedirectToOffline(RedirectResult result,
-                                    const GURL& online_url);
-  void SelectBestPageForRedirectToOffline(
+  void GetBestPageForRedirectToOffline(RedirectResult result,
+                                       const GURL& online_url);
+  void GetBestPageForOnlineURLDone(

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

the name doesn't match what this method does now. 
Maybe ContinueRedirectToOfflinePage?

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

Per discussion, changed to SelectPageForOnlineURLDone.

       RedirectResult result,
       const GURL& online_url,
-      const MultipleOfflinePageItemResult& pages);
+      const OfflinePageItem* offline_page);
   void TryRedirectToOffline(RedirectResult result,
                             const GURL& from_url,
                             const OfflinePageItem& offline_page);
 
   void Redirect(const GURL& from_url, const GURL& to_url);
 
   // Returns true if a given URL is in redirect chain already.
   bool IsInRedirectLoop(const GURL& to_url) const;
 
   void ReportRedirectResultUMA(RedirectResult result);
 
   // Iff the tab we are associated with is redirected to an offline page,
   // |offline_page_| will be non-null.  This can be used to synchronously ask
   // about the offline state of the current web contents.
   std::unique_ptr<OfflinePageItem> offline_page_;
   std::unique_ptr<Delegate> delegate_;
 
   base::WeakPtrFactory<OfflinePageTabHelper> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(OfflinePageTabHelper);
 };
 
 }  // namespace offline_pages
 
 #endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_TAB_HELPER_H_