[Offline pages] Adding in memory request queue store with tests

components/offline_pages/background/request_queue_store.h

Index: components/offline_pages/background/request_queue_store.h
diff --git a/components/offline_pages/background/request_queue_store.h b/components/offline_pages/background/request_queue_store.h
new file mode 100644
index 0000000000000000000000000000000000000000..076430a139fe3fb716c06c35ec59527bf37fd72e
--- /dev/null
+++ b/components/offline_pages/background/request_queue_store.h
@@ -0,0 +1,60 @@
+// 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_REQUEST_QUEUE_STORE_H_
+#define COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_QUEUE_STORE_H_
+
+#include <stdint.h>
+#include <vector>
+
+#include "base/callback.h"
+
+namespace offline_pages {
+
+class SavePageRequest;
+
+// Interface for classes storing save page requests.
+class RequestQueueStore {
+ public:
+  enum class UpdateStatus {
+    kAdded,    // Request was added successfully.
+    kUpdated,  // Request was updated successfully.
+    kFailed,   // Add or update attempt failed.
+  };
+
+  typedef base::Callback<void(
+      bool /* success */,
+      const std::vector<SavePageRequest>& /* requests */)>
+      GetRequestsCallback;
+  typedef base::Callback<void(UpdateStatus)> UpdateCallback;
+  typedef base::Callback<void(bool /* success */,
+                              int /* number of deleted requests */)>
+      RemoveCallback;
+  typedef base::Callback<void(bool /* success */)> ResetCallback;
+
+  virtual ~RequestQueueStore(){};
+
+  // Gets all of the requests from the store.
+  virtual void GetRequests(const GetRequestsCallback& callback) = 0;
+
+  // Asynchronously adds or updates request in store.
+  // Result of the update is passed in the callback.
+  virtual void AddOrUpdateRequest(const SavePageRequest& request,
+                                  const UpdateCallback& callback) = 0;
+
+  // Asynchronously removes requests from the store using their IDs.
+  // Result of the update, and a number of removed pages is passed in the
+  // callback.
+  // Result of remove should be false, when one of the provided items couldn't
+  // be deleted, e.g. because it was missing.
+  virtual void RemoveRequests(const std::vector<int64_t>& request_ids,
+                              const RemoveCallback& callback) = 0;
+
+  // Resets the store.
+  virtual void Reset(const ResetCallback& callback) = 0;
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_QUEUE_STORE_H_