bpf_dsl: Move {Bool,Result}ExprImpl definition into separate header

sandbox/linux/bpf_dsl/bpf_dsl.cc

 // 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.
 
 #include "sandbox/linux/bpf_dsl/bpf_dsl.h"
 
 #include <errno.h>
 
 #include <limits>
 
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
+#include "sandbox/linux/bpf_dsl/bpf_dsl_impl.h"
 #include "sandbox/linux/seccomp-bpf/errorcode.h"
 #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
 #include "sandbox/linux/seccomp-bpf/syscall_iterator.h"
 
 namespace sandbox {
 namespace bpf_dsl {
 namespace {
 
 class AllowResultExprImpl : public internal::ResultExprImpl {
  public:
@@ skipping 374 matching lines @@
   }
   return InvalidSyscall()->HasUnsafeTraps();
 }
 
 ResultExpr SandboxBPFDSLPolicy::Trap(Trap::TrapFnc trap_func, const void* aux) {
   return bpf_dsl::Trap(trap_func, aux);
 }
 
 }  // namespace bpf_dsl
 }  // namespace sandbox
+
+template class scoped_refptr<const sandbox::bpf_dsl::internal::BoolExprImpl>;
+template class scoped_refptr<const sandbox::bpf_dsl::internal::ResultExprImpl>;