AU: Don't send no-op operations in the delta payload.

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 193 matching lines @@
       Graph* graph,
       const std::string& new_kernel_part,
       const std::string& new_image,
       off_t image_size,
       int fd,
       off_t* data_file_size,
       off_t chunk_size,
       std::vector<DeltaArchiveManifest_InstallOperation>* kernel_ops,
       std::vector<Vertex::Index>* final_order);
 
+  // Returns true if |op| is a no-op operation that doesn't do any useful work
+  // (e.g., a move operation that copies blocks onto themselves).
+  static bool IsNoopOperation(const DeltaArchiveManifest_InstallOperation& op);
+
  private:
   // This should never be constructed
   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__