[Offline Pages] Turn Offliner::Cancel into an async operation to resolve conflicting assumptions

chrome/browser/android/offline_pages/background_loader_offliner.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_BACKGROUND_LOADER_OFFLINER_H_
 #define CHROME_BROWSER_ANDROID_OFFLINE_PAGES_BACKGROUND_LOADER_OFFLINER_H_
 
 #include <memory>
 
 #include "base/android/application_status_listener.h"
@@ skipping 19 matching lines @@
                                  public content::WebContentsObserver {
  public:
   BackgroundLoaderOffliner(content::BrowserContext* browser_context,
                            const OfflinerPolicy* policy,
                            OfflinePageModel* offline_page_model);
   ~BackgroundLoaderOffliner() override;
 
   // Offliner implementation.
   bool LoadAndSave(const SavePageRequest& request,
                    const CompletionCallback& callback) override;
-  void Cancel() override;
+  void Cancel(const CancelCallback& callback) override;
 
   // WebContentsObserver implementation.
   void DidStopLoading() override;
   void RenderProcessGone(base::TerminationStatus status) override;
   void WebContentsDestroyed() override;
   void DidFinishNavigation(
       content::NavigationHandle* navigation_handle) override;
 
  protected:
   // Called to reset internal loader and observer state.
   virtual void ResetState();
 
  private:
   friend class TestBackgroundLoaderOffliner;
 
   enum SaveState { NONE, SAVING, DELETE_AFTER_SAVE };
   enum PageLoadState { SUCCESS, RETRIABLE, NONRETRIABLE };
 
   // Called when the page has been saved.
   void OnPageSaved(SavePageResult save_result, int64_t offline_id);
 
   // Called when application state has changed.
   void OnApplicationStateChange(
       base::android::ApplicationState application_state);
+  void HandleApplicationStateChangeCancel(const SavePageRequest& request,
+                                          int64_t offline_id);
 
   std::unique_ptr<background_loader::BackgroundLoaderContents> loader_;
   // Not owned.
   content::BrowserContext* browser_context_;
   // Not owned.
   OfflinePageModel* offline_page_model_;
   // Tracks pending request, if any.
   std::unique_ptr<SavePageRequest> pending_request_;
   // Callback when pending request completes.
   CompletionCallback completion_callback_;
   // ApplicationStatusListener to monitor if Chrome moves to the foreground.
   std::unique_ptr<base::android::ApplicationStatusListener> app_listener_;
   // Whether we are on a low-end device.
   bool is_low_end_device_;
+
   // Save state.
   SaveState save_state_;
   // Page load state.
   PageLoadState page_load_state_;
 
+  // Callback for cancel.
+  CancelCallback cancel_callback_;
+
   base::WeakPtrFactory<BackgroundLoaderOffliner> weak_ptr_factory_;
   DISALLOW_COPY_AND_ASSIGN(BackgroundLoaderOffliner);
 };
 
 }  // namespace offline_pages
 #endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_BACKGROUND_LOADER_OFFLINER_H_