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

content/browser/download/download_item_impl_delegate.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_DOWNLOAD_ITEM_IMPL_DELEGATE_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_IMPL_DELEGATE_H_
 
 #include <stdint.h>
 
 #include "base/callback.h"
@@ skipping 51 matching lines @@
 
   // Tests if a file type should be opened automatically.
   virtual bool ShouldOpenFileBasedOnExtension(const base::FilePath& path);
 
   // Checks whether a downloaded file still exists and updates the
   // file's state if the file is already removed.
   // The check may or may not result in a later asynchronous call
   // to OnDownloadedFileRemoved().
   virtual void CheckForFileRemoval(DownloadItemImpl* download_item);
 
+  // Return a GUID string used for identifying the application to the system AV
+  // function for scanning downloaded files. If an empty or invalid GUID string
+  // is returned, no client identification will be given to the AV function.
+  virtual std::string GetApplicationClientIdForFileScanning() const;
+
   // Called when an interrupted download is resumed.
   virtual void ResumeInterruptedDownload(
       scoped_ptr<content::DownloadUrlParameters> params,
       uint32_t id);
 
   // For contextual issues like language and prefs.
   virtual BrowserContext* GetBrowserContext() const;
 
   // Update the persistent store with our information.
   virtual void UpdatePersistence(DownloadItemImpl* download);
@@ skipping 14 matching lines @@
  private:
   // For "Outlives attached DownloadItemImpl" invariant assertion.
   int count_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadItemImplDelegate);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_IMPL_DELEGATE_H_