[Offline pages] Introduction of MarkAttemptStartedTask with tests

components/offline_pages/background/mark_attempt_started_task.h

Index: components/offline_pages/background/mark_attempt_started_task.h
diff --git a/components/offline_pages/background/mark_attempt_started_task.h b/components/offline_pages/background/mark_attempt_started_task.h
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+++ b/components/offline_pages/background/mark_attempt_started_task.h
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+// 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 COMPONENTS_OFFLINE_PAGES_BACKGROUND_MARK_ATTEMPT_STARTED_TASK_H_
+#define COMPONENTS_OFFLINE_PAGES_BACKGROUND_MARK_ATTEMPT_STARTED_TASK_H_
+
+#include <stdint.h>
+
+#include <memory>
+#include <unordered_set>
+#include <vector>
+
+#include "base/memory/weak_ptr.h"
+#include "components/offline_pages/background/request_queue_store.h"
+#include "components/offline_pages/background/save_page_request.h"
+#include "components/offline_pages/core/task.h"
+
+namespace offline_pages {
+
+class MarkAttemptStartedTask : public Task {
+ public:
+  MarkAttemptStartedTask(RequestQueueStore* store,
+                         int64_t request_id,
+                         const RequestQueueStore::UpdateCallback& callback);
+  ~MarkAttemptStartedTask() override;
+
+  // TaskQueue::Task implementation.
+  void Run() override;
+
+ private:
+  // Step 1. Reading the requests.
+  void ReadRequest();
+  // Step 2. Verifies item exists, marks started and saves.
+  void MarkAttemptStarted(std::unique_ptr<UpdateRequestsResult> result);
+  // Step 3. Completes once update is done.
+  void CompleteWithResult(std::unique_ptr<UpdateRequestsResult> result);
+
+  // Store that this task updates. Not owned.
+  RequestQueueStore* store_;
+  // Request ID of the request to be started.
+  int64_t request_id_;
+  // Callback to complete the task.
+  RequestQueueStore::UpdateCallback callback_;
+
+  base::WeakPtrFactory<MarkAttemptStartedTask> weak_ptr_factory_;
+  DISALLOW_COPY_AND_ASSIGN(MarkAttemptStartedTask);
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_MARK_ATTEMPT_STARTED_TASK_H_