Serve offline page for online URL on disconnected or bad networks

chrome/browser/android/offline_pages/offline_page_request_handler.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_REQUEST_HANDLER_H_
-#define CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_REQUEST_HANDLER_H_
-
-#include "base/macros.h"
-#include "base/supports_user_data.h"
-#include "content/public/common/resource_type.h"
-
-namespace net {
-class NetworkDelegate;
-class URLRequest;
-class URLRequestInterceptor;
-class URLRequestJob;
-}
-
-namespace offline_pages {
-
-// Class for servicing requests based on their offline information. Created one
-// per URLRequest and attached to each request.
-//
-// For each supported profile, OfflinePageRequestHandler::CreateInterceptor
-// should be called once to install the custom interceptor.
-//
-// For each request:
-// 1) When a request is starting, OfflinePageRequestHandler::InitializeHandler
-//    will be called to create a new handler and attach to the request.
-// 2) When a request is being processed, MaybeInterceptRequest of custom
-//    interceptor will be inquired.
-//    2.1) If the attached OfflinePageRequestHandler for the request is found,
-//         delegate to OfflinePageRequestHandler::MaybeCreateJob to do the work.
-//         2.1.1) Do immediate checks for those scenarios that the interception
-//                is not needed. Bail out if so.
-//         2.1.2) Start an async task to try to find the offline page.
-//         2.1.3) Return a custom URLRequestJob that is put on hold to wait
-//                for the result of finding offline page.
-//    2.2) Otherwise, bail out without interception.
-class OfflinePageRequestHandler : public base::SupportsUserData::Data {
- public:
-  // Attaches a newly created handler if the given |request| needs to
-  // be handled by offline pages.
-  static void InitializeHandler(net::URLRequest* request,
-                                content::ResourceType resource_type);
-
-  // Returns the handler attached to |request|. This may return null if no
-  // handler is attached.
-  static OfflinePageRequestHandler* GetHandler(net::URLRequest* request);
-
-  // Creates a protocol interceptor for offline pages. Created one per
-  // supported, i.e. non-incognito, profile.
-  // |profile_id|, which identifies the profile, is passed as a void* to ensure
-  // it's not accidently used on the IO thread.
-  static std::unique_ptr<net::URLRequestInterceptor> CreateInterceptor(
-      void* profile_id);
-
-  ~OfflinePageRequestHandler() override;
-
-  net::URLRequestJob* MaybeCreateJob(
-      net::URLRequest* request,
-      net::NetworkDelegate* network_delegate,
-      void* profile_id);
-
- private:
-  OfflinePageRequestHandler();
-
-  DISALLOW_COPY_AND_ASSIGN(OfflinePageRequestHandler);
-};
-
-}  // namespace offline_pages
-
-#endif // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_REQUEST_HANDLER_H_