AU: delta compress the kernel partition

src/platform/update_engine/delta_diff_generator.h

Index: src/platform/update_engine/delta_diff_generator.h
diff --git a/src/platform/update_engine/delta_diff_generator.h b/src/platform/update_engine/delta_diff_generator.h
index bbaa473cb76c54c1e2437b12fa6f6ab68be7148c..efc47478fe4b518867a0a4a3124bebd0fed7a5df 100644
--- a/src/platform/update_engine/delta_diff_generator.h
+++ b/src/platform/update_engine/delta_diff_generator.h
@@ -40,12 +40,16 @@ class DeltaDiffGenerator {
   // This is the only function that external users of the class should call.
   // old_image and new_image are paths to two image files. They should be
   // mounted read-only at paths old_root and new_root respectively.
+  // {old,new}_kernel_part are paths to the old and new kernel partition
+  // images, respectively.
   // output_path is the filename where the delta update should be written.
   // Returns true on success.
   static bool GenerateDeltaUpdateFile(const std::string& old_root,
                                       const std::string& old_image,
                                       const std::string& new_root,
                                       const std::string& new_image,
+                                      const std::string& old_kernel_part,
+                                      const std::string& new_kernel_part,
                                       const std::string& output_path);
 
   // These functions are public so that the unit tests can access them: