Add request header on gdata operation for testing ETag match.

chrome/browser/chromeos/drive/drive_api_service.h

Index: chrome/browser/chromeos/drive/drive_api_service.h
diff --git a/chrome/browser/chromeos/drive/drive_api_service.h b/chrome/browser/chromeos/drive/drive_api_service.h
index fd1ff0ed0b25603d14407eae9a34472530349707..d9c6e46dcebd50128185259893f6cfd2cef05d75 100644
--- a/chrome/browser/chromeos/drive/drive_api_service.h
+++ b/chrome/browser/chromeos/drive/drive_api_service.h
@@ -64,17 +64,20 @@ class DriveAPIService : public DriveServiceInterface,
       const gdata::GetDataCallback& callback) OVERRIDE;
   virtual void DeleteDocument(
       const GURL& document_url,
+      const std::string& etag,
       const gdata::EntryActionCallback& callback) OVERRIDE;
   virtual void DownloadDocument(
       const FilePath& virtual_path,
       const FilePath& local_cache_path,
       const GURL& content_url,
       DocumentExportFormat format,
+      const std::string& etag,
       const gdata::DownloadActionCallback& callback) OVERRIDE;
   virtual void DownloadFile(
       const FilePath& virtual_path,
       const FilePath& local_cache_path,
       const GURL& content_url,
+      const std::string& etag,
       const gdata::DownloadActionCallback& download_action_callback,
       const gdata::GetContentCallback& get_content_callback) OVERRIDE;
   virtual void CopyDocument(const std::string& resource_id,