Cleanup remaining class/struct fwd declarations

sandbox/linux/bpf_dsl/bpf_dsl.h

 // Copyright 2014 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_BPF_DSL_BPF_DSL_H_
 #define SANDBOX_LINUX_BPF_DSL_BPF_DSL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 58 matching lines @@
 // The semantics of each function and operator are intended to be
 // intuitive, but are described in more detail below.
 //
 // (Credit to Sean Parent's "Inheritance is the Base Class of Evil"
 // talk at Going Native 2013 for promoting value semantics via shared
 // pointers to immutable state.)
 
 namespace sandbox {
 namespace bpf_dsl {
 
+template <typename T>
+class Caser;
+
+class Elser;
+
 // ResultExpr is an opaque reference to an immutable result expression tree.
 using ResultExpr = std::shared_ptr<const internal::ResultExprImpl>;
 
 // BoolExpr is an opaque reference to an immutable boolean expression tree.
 using BoolExpr = std::shared_ptr<const internal::BoolExprImpl>;
 
 // Allow specifies a result that the system call should be allowed to
 // execute normally.
 SANDBOX_EXPORT ResultExpr Allow();
 
@@ skipping 237 matching lines @@
 
 template <typename... Rest>
 BoolExpr AnyOf(BoolExpr first, Rest&&... rest) {
   return AnyOf(std::move(first), AnyOf(std::forward<Rest>(rest)...));
 }
 
 }  // namespace bpf_dsl
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_BPF_DSL_BPF_DSL_H_