Return operation name in prefetch request callback and add internal page hookup

components/offline_pages/core/prefetch/prefetch_proto_utils.h

 // Copyright 2017 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_CORE_PREFETCH_PREFETCH_PROTO_UTILS_H_
 #define COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_PREFETCH_PROTO_UTILS_H_
 
+#include <string>
 #include <vector>
 #include "components/offline_pages/core/prefetch/prefetch_types.h"
 
 namespace offline_pages {
 
 // The fully qualified type name for PageBundle defined in proto.
 extern const char kPageBundleTypeURL[];
 
-// Used to parse the Operation serialized in binary proto |data|.
-bool ParseOperationResponse(const std::string& data,
-                            std::vector<RenderPageInfo>* pages);
+// Parse the Operation serialized in binary proto |data|. Returns the operation
+// name if parsing succeeded. Otherwise, empty string is returned.
+std::string ParseOperationResponse(const std::string& data,
+                                   std::vector<RenderPageInfo>* pages);
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_PREFETCH_PROTO_UTILS_H_