AU: Push seeks in http fetching to the progress percentage.

http_fetcher.h

 // Copyright (c) 2009 The Chromium OS 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 CHROMEOS_PLATFORM_UPDATE_ENGINE_HTTP_FETCHER_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_HTTP_FETCHER_H__
 
 #include <string>
 #include <vector>
 #include <glib.h>
@@ skipping 71 matching lines @@
 
   // The delegate; may be NULL.
   HttpFetcherDelegate* delegate_;
  private:
   DISALLOW_COPY_AND_ASSIGN(HttpFetcher);
 };
 
 // Interface for delegates
 class HttpFetcherDelegate {
  public:
-  // Called every time bytes are received, even if they are automatically
-  // delivered to an output file.
+  // Called every time bytes are received.
   virtual void ReceivedBytes(HttpFetcher* fetcher,
                              const char* bytes,
                              int length) = 0;
 
+  // Called if the fetcher seeks to a particular offset.
+  virtual void SeekToOffset(off_t offset) {}
+
   // Called when the transfer has completed successfully or been somehow
   // aborted.
   virtual void TransferComplete(HttpFetcher* fetcher, bool successful) = 0;
 };
 
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_HTTP_FETCHER_H__