[Offline pages] Filter out pages cached by different tabs on tab helper

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 "components/offline_pages/offline_page_types.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 #include "url/gurl.h"
 
 namespace content {
 class WebContents;
 }
 
 namespace offline_pages {
 
 struct OfflinePageItem;
 
 // Per-tab class to manage switch between online version and offline version.
 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;
+  };
+
   ~OfflinePageTabHelper() override;
 
   const OfflinePageItem* offline_page() { return offline_page_.get(); }
 
  private:
   enum class RedirectReason {
     DISCONNECTED_NETWORK,
     FLAKY_NETWORK,
     FLAKY_NETWORK_FORWARD_BACK
   };
 
   friend class content::WebContentsUserData<OfflinePageTabHelper>;
   friend class OfflinePageTabHelperTest;
   FRIEND_TEST_ALL_PREFIXES(OfflinePageTabHelperTest,
                            NewNavigationCancelsPendingRedirects);
 
   explicit OfflinePageTabHelper(content::WebContents* web_contents);
 
+  void SetDelegateForTesting(std::unique_ptr<Delegate> delegate);
+
   // Overridden from content::WebContentsObserver:
   void DidStartNavigation(
       content::NavigationHandle* navigation_handle) override;
   void DidFinishNavigation(
       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.
+  void GetPagesForRedirectToOffline(const GURL& online_url,
+                                    RedirectReason reason);
+  void SelectBestPageForRedirectToOffline(
+      const GURL& online_url,
+      RedirectReason reason,
+      const MultipleOfflinePageItemResult& pages);
   void TryRedirectToOffline(RedirectReason redirect_reason,
                             const GURL& from_url,
-                            const OfflinePageItem* offline_page);
+                            const OfflinePageItem& offline_page);
 
   void Redirect(const GURL& from_url, const GURL& to_url);
 
   // 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_