Serve offline page for online URL on disconnected or bad networks

chrome/browser/android/offline_pages/offline_page_request_job.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_JOB_H_
+#define CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_REQUEST_JOB_H_
+
+#include "base/memory/weak_ptr.h"
+#include "net/url_request/url_request_file_job.h"
+
+namespace base {
+class FilePath;
+}
+
+namespace offline_pages {
+
+// A request job that serves content from offline file.
+class OfflinePageRequestJob : public net::URLRequestFileJob {
+ public:
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    // Will be invoked before the request is restarted. The request handler
+    // which implements this delegate, can use this opportunity to set a
+    // specific state in order to prevent the request from being intercepted.
+    virtual void OnPrepareToRestart() = 0;
+  };
+
+  OfflinePageRequestJob(net::URLRequest* request,
+                        net::NetworkDelegate* network_delegate,
+                        Delegate* delegate);
+  ~OfflinePageRequestJob() override;
+
+  // net::URLRequestJob overrides:
+  void Start() override;
+  void Kill() override;
+
+  base::WeakPtr<OfflinePageRequestJob> GetWeakPtr();
+
+  // Callback to fall back to default handling when offline file is not found.
+  void FallbackToDefault();
+
+  // Called when offline file is found.
+  void SetOfflineFilePath(const base::FilePath& offline_file_path);
+
+ private:
+  // Enum state controls how the job should be processed.
+  enum class State {
+    // Waiting to get the offline page info for the URL.
+    NOT_DETERMINED,
+    // Needs to restart the request in order to fall back to the default
+    // handling when no offline page is found.
+    FALLBACK_TO_DEFAULT,
+    // Serves the offline content.
+    SHOW_OFFLINE_CONTENT
+  };
+
+  // Processes the request based on current state.
+  void MaybeStartRequest();
+
+  Delegate* delegate_;  // Not owned.
+  bool is_started_;
+  State state_;
+  base::WeakPtrFactory<OfflinePageRequestJob> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(OfflinePageRequestJob);
+};
+
+}  // namespace offline_pages
+
+#endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_REQUEST_JOB_H_