Update from https://crrev.com/306655

sandbox/linux/seccomp-bpf/codegen.h

 // Copyright (c) 2012 The Chromium 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 SANDBOX_LINUX_SECCOMP_BPF_CODEGEN_H__
 #define SANDBOX_LINUX_SECCOMP_BPF_CODEGEN_H__
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 88 matching lines @@
   // logical beginning) of |program_|.
   Node Append(uint16_t code, uint32_t k, size_t jt, size_t jf);
 
   // Offset returns how many instructions exist in |program_| after |target|.
   size_t Offset(Node target) const;
 
   // NOTE: program_ is the compiled program in *reverse*, so that
   // indices remain stable as we add instructions.
   Program program_;
 
+  // equivalent_ stores the most recent semantically-equivalent node for each
+  // instruction in program_. A node is defined as semantically-equivalent to N
+  // if it has the same instruction code and constant as N and its successor
+  // nodes (if any) are semantically-equivalent to N's successor nodes, or
+  // if it's an unconditional jump to a node semantically-equivalent to N.
+  std::vector<Node> equivalent_;
+
   std::map<MemoKey, Node, MemoKeyLess> memos_;
 
   DISALLOW_COPY_AND_ASSIGN(CodeGen);
 };
 
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SECCOMP_BPF_CODEGEN_H__