Serve offline page for online URL on disconnected or bad networks

chrome/browser/android/offline_pages/offline_page_request_job.cc

+// 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.
+
+#include "chrome/browser/android/offline_pages/offline_page_request_job.h"
+
+#include "base/bind.h"
+#include "base/files/file_path.h"
+#include "base/logging.h"
+#include "content/public/browser/browser_thread.h"
+#include "net/http/http_request_headers.h"
+#include "net/url_request/url_request.h"
+
+using content::BrowserThread;
+
+namespace offline_pages {
+
+OfflinePageRequestJob::OfflinePageRequestJob(
+    net::URLRequest* request,
+    net::NetworkDelegate* network_delegate,
+    Delegate* delegate)
+    : net::URLRequestFileJob(
+          request,
+          network_delegate,
+          base::FilePath(),
+          BrowserThread::GetBlockingPool()->GetTaskRunnerWithShutdownBehavior(
+              base::SequencedWorkerPool::SKIP_ON_SHUTDOWN)),
+      delegate_(delegate),
+      is_started_(false),
+      state_(State::NOT_DETERMINED),
+      weak_ptr_factory_(this) {
+}
+
+OfflinePageRequestJob::~OfflinePageRequestJob() {
+}
+
+void OfflinePageRequestJob::Start() {
+  MaybeStartRequest();
+}
+
+void OfflinePageRequestJob::Kill() {
+  net::URLRequestJob::Kill();
+  weak_ptr_factory_.InvalidateWeakPtrs();
+}
+
+base::WeakPtr<OfflinePageRequestJob> OfflinePageRequestJob::GetWeakPtr() {
+  return weak_ptr_factory_.GetWeakPtr();
+}
+
+void OfflinePageRequestJob::FallbackToDefault() {
+  state_ = State::FALLBACK_TO_DEFAULT;
+  MaybeStartRequest();
+}
+
+void OfflinePageRequestJob::SetOfflineFilePath(
+    const base::FilePath& offline_file_path) {
+  DCHECK(!offline_file_path.empty());
+
+  state_ = State::SHOW_OFFLINE_CONTENT;
+  file_path_ = offline_file_path;
+  URLRequestFileJob::Start();
+}
+
+void OfflinePageRequestJob::MaybeStartRequest() {
+  if (is_started_)
+    return;
+
+  switch (state_) {
+    case State::NOT_DETERMINED:
+      // Still waiting to get offline data.
+      return;
+    case State::FALLBACK_TO_DEFAULT:
+      // Restart the request to create a new job. Our request handler will
+      // return nullptr, and the default job should be created.
+      is_started_ = false;
+      delegate_->OnPrepareToRestart();
+      URLRequestJob::NotifyRestartRequired();
+      return;
+    case State::SHOW_OFFLINE_CONTENT:
+      is_started_ = true;
+      NotifyHeadersComplete();
+      return;
+  }
+
+  NOTREACHED();
+}
+
+}  // namespace offline_pages