[Offline Prefetech] Send GetOperationReqest to the server

components/offline_pages/core/prefetch/prefetch_request_fetcher.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_REQUEST_FETCHER_H_
 #define COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_PREFETCH_REQUEST_FETCHER_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "components/offline_pages/core/prefetch/prefetch_types.h"
 #include "net/url_request/url_fetcher_delegate.h"
 
-class GURL;
 namespace net {
 class URLRequestContextGetter;
 }
 
 namespace offline_pages {
 
+// Asynchronously fetches the offline prefetch related data from the server.
 class PrefetchRequestFetcher : public net::URLFetcherDelegate {
  public:
   using FinishedCallback = base::Callback<void(PrefetchRequestStatus status,
                                                const std::string& data)>;
 
-  PrefetchRequestFetcher(const GURL& url,
+  // If |message| is empty, the GET request is sent. Otherwise, the POST request
+  // is sent with |message| as post data.
+  PrefetchRequestFetcher(const std::string& url_path,

[dewittj, 2017/05/16 18:30:20]

Can you make two constructors, one that is for posting data, and one for get? 

[jianli, 2017/05/16 22:44:40]

Changed to 2 static creator methods since their names are even clearer than
different constructors.

                          const std::string& message,
                          net::URLRequestContextGetter* request_context_getter,
                          const FinishedCallback& callback);
   ~PrefetchRequestFetcher() override;
 
   // URLFetcherDelegate implementation.
   void OnURLFetchComplete(const net::URLFetcher* source) override;
 
  private:
   PrefetchRequestStatus ParseResponse(const net::URLFetcher* source,
                                       std::string* data);
 
   scoped_refptr<net::URLRequestContextGetter> request_context_getter_;
   std::unique_ptr<net::URLFetcher> url_fetcher_;
   FinishedCallback callback_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefetchRequestFetcher);
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_PREFETCH_REQUEST_FETCHER_H_