AU: Really delta compress the kernel if an old kernel is provided.

delta_diff_generator.h

 // Copyright (c) 2010 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_DELTA_DIFF_GENERATOR_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_DELTA_DIFF_GENERATOR_H__
 
 #include <string>
 #include <vector>
 #include "base/basictypes.h"
@@ skipping 79 matching lines @@
   // the smallest way to encode this file for the diff. It stores
   // necessary data in out_data and fills in out_op.
   // If there's no change in old and new files, it creates a MOVE
   // operation. If there is a change, or the old file doesn't exist,
   // the smallest of REPLACE, REPLACE_BZ, or BSDIFF wins.
   // new_filename must contain at least one byte.
   // Returns true on success.
   static bool ReadFileToDiff(const std::string& old_filename,
                              const std::string& new_filename,
                              std::vector<char>* out_data,
-                             DeltaArchiveManifest_InstallOperation* out_op);
+                             DeltaArchiveManifest_InstallOperation* out_op,
+                             bool gather_extents);
 
   // Modifies blocks read by 'op' so that any blocks referred to by
   // 'remove_extents' are replaced with blocks from 'replace_extents'.
   // 'remove_extents' and 'replace_extents' must be the same number of blocks.
   // Blocks will be substituted in the order listed in the vectors.
   // E.g. if 'op' reads blocks 1, 2, 3, 4, 5, 6, 7, 8, remove_extents
   // contains blocks 6, 2, 3, 5, and replace blocks contains
   // 12, 13, 14, 15, then op will be changed to read from:
   // 1, 13, 14, 4, 15, 12, 7, 8
   static void SubstituteBlocks(Vertex* vertex,
@@ skipping 104 matching lines @@
   DISALLOW_IMPLICIT_CONSTRUCTORS(DeltaDiffGenerator);
 };
 
 extern const char* const kBsdiffPath;
 extern const char* const kBspatchPath;
 extern const char* const kDeltaMagic;
 
 };  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_DELTA_DIFF_GENERATOR_H__