bpf_dsl: replace scoped_refptr with std::shared_ptr

sandbox/linux/bpf_dsl/bpf_dsl_impl.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_IMPL_H_
 #define SANDBOX_LINUX_BPF_DSL_BPF_DSL_IMPL_H_
 
+#include <memory>
+
 #include "base/macros.h"
-#include "base/memory/ref_counted.h"
 #include "sandbox/linux/bpf_dsl/codegen.h"
 #include "sandbox/sandbox_export.h"
 
 namespace sandbox {
 namespace bpf_dsl {
 class ErrorCode;
 class PolicyCompiler;
 
 namespace internal {
 
 // Internal interface implemented by BoolExpr implementations.
-class BoolExprImpl : public base::RefCounted<BoolExprImpl> {
+class BoolExprImpl {
  public:
   // Compile uses |pc| to emit a CodeGen::Node that conditionally continues
   // to either |then_node| or |false_node|, depending on whether the represented
   // boolean expression is true or false.
   virtual CodeGen::Node Compile(PolicyCompiler* pc,
                                 CodeGen::Node then_node,
                                 CodeGen::Node else_node) const = 0;
 
  protected:
   BoolExprImpl() {}
   virtual ~BoolExprImpl() {}
 
  private:
-  friend class base::RefCounted<BoolExprImpl>;
   DISALLOW_COPY_AND_ASSIGN(BoolExprImpl);
 };
 
 // Internal interface implemented by ResultExpr implementations.
-class ResultExprImpl : public base::RefCounted<ResultExprImpl> {
+class ResultExprImpl {
  public:
   // Compile uses |pc| to emit a CodeGen::Node that executes the
   // represented result expression.
   virtual CodeGen::Node Compile(PolicyCompiler* pc) const = 0;
 
   // HasUnsafeTraps returns whether the result expression is or recursively
   // contains an unsafe trap expression.
   virtual bool HasUnsafeTraps() const;
 
   // IsAllow returns whether the result expression is an "allow" result.
   virtual bool IsAllow() const;
 
   // IsAllow returns whether the result expression is a "deny" result.
   virtual bool IsDeny() const;
 
  protected:
   ResultExprImpl() {}
   virtual ~ResultExprImpl() {}
 
  private:
-  friend class base::RefCounted<ResultExprImpl>;
   DISALLOW_COPY_AND_ASSIGN(ResultExprImpl);
 };
 
 }  // namespace internal
 }  // namespace bpf_dsl
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_BPF_DSL_BPF_DSL_IMPL_H_