[Offline pages] Extracting AddRequest method in RequestQueueStore

components/offline_pages/background/request_queue.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 COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_QUEUE_H_
 #define COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_QUEUE_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 14 matching lines @@
 class RequestQueue {
  public:
   enum class GetRequestsResult {
     SUCCESS,
     STORE_FAILURE,
   };
 
   enum class AddRequestResult {
     SUCCESS,
     STORE_FAILURE,
+    ALREADY_EXISTS,
     REQUEST_QUOTA_HIT,  // Cannot add a request with this namespace, as it has
                         // reached a quota of active requests.
   };
 
   // GENERATED_JAVA_ENUM_PACKAGE:org.chromium.components.offlinepages.background
   enum class UpdateRequestResult {
     SUCCESS,
     STORE_FAILURE,
     REQUEST_DOES_NOT_EXIST,  // Failed to delete the request because it does not
                              // exist.
@@ skipping 82 matching lines @@
 
   // Allows us to pass a weak pointer to callbacks.
   base::WeakPtrFactory<RequestQueue> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RequestQueue);
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_QUEUE_H_