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 "content/public/common/resource_type.h"
+#include "net/url_request/url_request_file_job.h"
+
+namespace base {
+class FilePath;
+}
+
+namespace offline_pages {
+
+// This enum is used for UMA reporting. It contains all possible outcomes of
+// handling requests that might service offline page in different network
+// conditions. Generally one of these outcomes will happen.
+// The fringe errors (like no OfflinePageModel, etc.) are not reported due
+// to their low probability.
+// NOTE: because this is used for UMA reporting, these values should not be
+// changed or reused; new values should be ended immediately before the MAX
+// value. Make sure to update the histogram enum
+// (OfflinePagesAggregatedRequestResult in histograms.xml) accordingly.
+// Public for testing.
+enum class AggregatedRequestResult {
+  SHOW_OFFLINE_ON_DISCONNECTED_NETWORK,
+  PAGE_NOT_FOUND_ON_DISCONNECTED_NETWORK,
+  SHOW_OFFLINE_ON_FLAKY_NETWORK,
+  PAGE_NOT_FOUND_ON_FLAKY_NETWORK,
+  SHOW_OFFLINE_ON_PROHIBITIVELY_SLOW_NETWORK,
+  PAGE_NOT_FOUND_ON_PROHIBITIVELY_SLOW_NETWORK,
+  PAGE_NOT_FRESH_ON_PROHIBITIVELY_SLOW_NETWORK,
+  SHOW_OFFLINE_ON_CONNECTED_NETWORK,
+  PAGE_NOT_FOUND_ON_CONNECTED_NETWORK,
+  NO_TAB_ID,
+  NO_WEB_CONTENTS,
+  SHOW_NET_ERROR_PAGE,
+  AGGREGATED_REQUEST_RESULT_MAX
+};
+
+// Header that indicates that the offline page should be loaded if it exists
+// regardless current network conditions. Its value is a comma/space separated
+// name-value pair that may provide reason or define custom behavior.
+extern const char kLoadingOfflinePageHeader[];
+// The name used in name-value pair of kLoadingOfflinePageHeader to denote the
+// reason for loading offline page.
+extern const char kLoadingOfflinePageReason[];
+// Possible values in name-value pair that denote the reason for loading offline
+// page.
+extern const char kLoadingOfflinePageDueToNetError[];
+
+// A request job that serves content from offline file.
+class OfflinePageRequestJob : public net::URLRequestFileJob {
+ public:
+  // Reports the aggregated result combining both request result and network
+  // state.
+  static void ReportAggregatedRequestResult(AggregatedRequestResult result);
+
+  // Creates and returns a job to serve the offline page. Nullptr is returned if
+  // offline page cannot be served.

[Dmitry Titov, 2016/08/20 01:08:14]

"cannot or should not be served" would better describe it.

[jianli, 2016/08/20 01:48:52]

Done.

+  static OfflinePageRequestJob* Create(void* profile_id,
+                                       net::URLRequest* request,
+                                       net::NetworkDelegate* network_delegate);
+
+  ~OfflinePageRequestJob() override;
+
+  // net::URLRequestJob overrides:
+  void Start() override;
+  void Kill() override;
+
+  void OnOfflineFilePathAvailable(const base::FilePath& offline_file_path);
+
+ private:
+  OfflinePageRequestJob(void* profile_id,
+                        net::URLRequest* request,
+                        net::NetworkDelegate* network_delegate);
+
+  void StartAsync();
+
+  // Restarts the request job in order to fall back to the default handling.
+  void FallbackToDefault();
+
+  // The profile for processing offline pages.
+  void* profile_id_;
+
+  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_