Add resource ID based download requests in {GDataWapi/Drive} requests.

chrome/browser/google_apis/drive_api_requests.h

 // Copyright (c) 2012 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 CHROME_BROWSER_GOOGLE_APIS_DRIVE_API_REQUESTS_H_
 #define CHROME_BROWSER_GOOGLE_APIS_DRIVE_API_REQUESTS_H_
 
 #include <string>
 
 #include "base/callback_forward.h"
@@ skipping 510 matching lines @@
   virtual void OnRangeRequestComplete(
       const UploadRangeResponse& response,
       scoped_ptr<base::Value> value) OVERRIDE;
 
  private:
   const UploadRangeCallback callback_;
 
   DISALLOW_COPY_AND_ASSIGN(GetUploadStatusRequest);
 };
 
+//========================== DownloadFileRequest ==========================
+
+// This class performs the request for downloading of a specified file.
+class DownloadFileRequest : public DownloadFileRequestBase {
+ public:
+  // See also DownloadFileRequestBase's comment for parameters meaning.
+  DownloadFileRequest(RequestSender* sender,
+                      const DriveApiUrlGenerator& url_generator,
+                      const std::string& resource_id,
+                      const base::FilePath& output_file_path,
+                      const DownloadActionCallback& download_action_callback,
+                      const GetContentCallback& get_content_callback,
+                      const ProgressCallback& progress_callback);
+  virtual ~DownloadFileRequest();
+
+  DISALLOW_COPY_AND_ASSIGN(DownloadFileRequest);
+};
 
 }  // namespace drive
 }  // namespace google_apis
 
 #endif  // CHROME_BROWSER_GOOGLE_APIS_DRIVE_API_REQUESTS_H_