[Downloads] Rework how hashes are calculated for download files.

content/browser/download/save_file.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 CONTENT_BROWSER_DOWNLOAD_SAVE_FILE_H_
 #define CONTENT_BROWSER_DOWNLOAD_SAVE_FILE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 20 matching lines @@
   DownloadInterruptReason Initialize();
   DownloadInterruptReason AppendDataToFile(const char* data, size_t data_len);
   DownloadInterruptReason Rename(const base::FilePath& full_path);
   void Detach();
   void Cancel();
   void Finish();
   void AnnotateWithSourceInformation();
   base::FilePath FullPath() const;
   bool InProgress() const;
   int64_t BytesSoFar() const;
-  bool GetHash(std::string* hash);
   std::string DebugString() const;
 
   // Accessors.
   SaveItemId save_item_id() const { return info_->save_item_id; }
   int render_process_id() const { return info_->render_process_id; }
   int request_id() const { return info_->request_id; }
   SaveFileCreateInfo::SaveFileSource save_source() const {
     return info_->save_source;
   }
 
  private:
   BaseFile file_;
   scoped_ptr<const SaveFileCreateInfo> info_;
 
   DISALLOW_COPY_AND_ASSIGN(SaveFile);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_SAVE_FILE_H_