AU: Implement exponential back off for 500 and 503 HTTP response codes.

download_action.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_DOWNLOAD_ACTION_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_DOWNLOAD_ACTION_H__
 
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
@@ skipping 58 matching lines @@
   typedef ActionTraits<DownloadAction>::InputObjectType InputObjectType;
   typedef ActionTraits<DownloadAction>::OutputObjectType OutputObjectType;
   void PerformAction();
   void TerminateProcessing();
 
   // Testing
   void SetTestFileWriter(FileWriter* writer) {
     writer_ = writer;
   }
 
+  int GetHTTPResponseCode() { return http_fetcher_->http_response_code(); }
+
   // Debugging/logging
   static std::string StaticType() { return "DownloadAction"; }
   std::string Type() const { return StaticType(); }
 
   // HttpFetcherDelegate methods (see http_fetcher.h)
   virtual void ReceivedBytes(HttpFetcher *fetcher,
                              const char* bytes, int length);
   virtual void TransferComplete(HttpFetcher *fetcher, bool successful);
 
   void set_delegate(DownloadActionDelegate* delegate) {
@@ skipping 30 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(DownloadAction);
 };
 
 // We want to be sure that we're compiled with large file support on linux,
 // just in case we find ourselves downloading large images.
 COMPILE_ASSERT(8 == sizeof(off_t), off_t_not_64_bit);
 
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_DOWNLOAD_ACTION_H__