Improve the page download:

chrome/browser/android/offline_pages/recent_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_RECENT_TAB_HELPER_H_
 #define CHROME_BROWSER_ANDROID_OFFLINE_PAGES_RECENT_TAB_HELPER_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/memory/weak_ptr.h"
+#include "components/offline_pages/downloads/download_ui_item.h"
 #include "components/offline_pages/offline_page_model.h"
 #include "components/offline_pages/snapshot_controller.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 NavigationEntry;
 class NavigationHandle;
 }
 
 namespace offline_pages {
 
 // Attaches to every WebContent shown in a tab. Waits until the WebContent is
 // loaded to proper degree and then makes a snapshot of the page. Removes the
 // oldest snapshot in the 'ring buffer'. As a result, there is always up to N
 // snapshots of recent pages on the device.
 class RecentTabHelper
     : public content::WebContentsObserver,
       public content::WebContentsUserData<RecentTabHelper>,
       public SnapshotController::Client {
  public:
   ~RecentTabHelper() override;
 
   // content::WebContentsObserver
   void DidFinishNavigation(
       content::NavigationHandle* navigation_handle) override;
   void DocumentAvailableInMainFrame() override;
   void DocumentOnLoadCompletedInMainFrame() override;
+  void WebContentsDestroyed() override;
 
   // SnapshotController::Client
   void StartSnapshot() override;
 
   // Delegate that is used by RecentTabHelper to get external dependencies.
   // Default implementation lives in .cc file, while tests provide an override.
   class Delegate {
    public:
     virtual ~Delegate() {}
     virtual std::unique_ptr<OfflinePageArchiver> CreatePageArchiver(
         content::WebContents* web_contents) = 0;
     virtual scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner() = 0;
     // There is no expectations that tab_id is always present.
     virtual bool GetTabId(content::WebContents* web_contents, int* tab_id) = 0;
   };
   void SetDelegate(std::unique_ptr<RecentTabHelper::Delegate> delegate);
 
-  bool is_page_ready_for_snapshot() const {
-    return is_page_ready_for_snapshot_;
-  }
+  // Support for Download Page feature. The Download Page button does this:
+  // 1. Creates suspended request for Background Offliner.
+  // 2. Calls this method with properly filled ClientId.
+  // 3. This tab helper observes the page load and captures the page
+  //    if the load progresses far enough, as indicated by SnapshotController.
+  // 4. If capture is successful, this tab helper removes the suspended request.
+  //    Otherwise (navigation to other page, close tab) tab helper un-suspends
+  //    the request so the Background Offliner starts working on it.
+  // 5. If Chrome is killed at any point, next time Background Offliner loads
+  //    it converts all suspended requests from last session into active.
+  void ObserveAndDownloadCurrentPage(const ClientId& client_id,
+                                     int64_t request_id);
 
  private:
+  // Keeps client_id/request_id that will be used for the offline snapshot.
+  struct DownloadPageInfo {
+   public:
+    DownloadPageInfo(const ClientId& client_id,
+                     int64_t request_id)
+        : client_id_(client_id),
+          request_id_(request_id),
+          page_snapshot_completed_(false) {}
+
+    // The ClientID to go with the offline page.
+    ClientId client_id_;
+    // Id of the suspended request in Background Offliner. Used to un-suspend
+    // the request if the capture of the current page was not possible (e.g.
+    // the user navigated to another page before current one was loaded).
+    // 0 if this is a "last_1" info.
+    int64_t request_id_;
+    // True if there was at least one snapshot successfully completed.
+    bool page_snapshot_completed_;
+  };
+
   explicit RecentTabHelper(content::WebContents* web_contents);
   friend class content::WebContentsUserData<RecentTabHelper>;
 
-
   void EnsureInitialized();
   void ContinueSnapshotWithIdsToPurge(const std::vector<int64_t>& page_ids);
   void ContinueSnapshotAfterPurge(OfflinePageModel::DeletePageResult result);
   void SavePageCallback(OfflinePageModel::SavePageResult result,
                         int64_t offline_id);
-
   void ReportSnapshotCompleted();
+  void ReportDownloadStatusToRequestCoordinator();
   bool IsSamePage() const;
-  ClientId client_id() const;
+  ClientId GetRecentPagesClientId() const;
 
   // Page model is a service, no ownership. Can be null - for example, in
   // case when tab is in incognito profile.
   OfflinePageModel* page_model_;
+
   // If false, never make snapshots off the attached WebContents.
   // Not page-specific.
   bool snapshots_enabled_;
+
   // Becomes true during navigation if the page is ready for snapshot as
   // indicated by at least one callback from SnapshotController.
   bool is_page_ready_for_snapshot_;
+
+  // Info for the offline page to capture. Null if the tab is not capturing
+  // current page.
+  std::unique_ptr<DownloadPageInfo> download_info_;
+
   // If empty, the tab does not have AndroidId and can not capture pages.
   std::string tab_id_;
 
   // The URL of the page that is currently being snapshotted. Used to check,
   // during async operations, that WebContents still contains the same page.
   GURL snapshot_url_;
   // This starts out null and used as a flag for EnsureInitialized() to do the
   // initialization only once.
   std::unique_ptr<SnapshotController> snapshot_controller_;
 
   std::unique_ptr<Delegate> delegate_;
 
   base::WeakPtrFactory<RecentTabHelper> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RecentTabHelper);
 };
 
 }  // namespace offline_pages
 #endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_RECENT_TAB_HELPER_H_