Make CPDF_ClipPath have a CPDF_ClipPathData rather than inheriting

core/fxcrt/include/cfx_count_ref.h

 // Copyright 2016 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef CORE_FXCRT_INCLUDE_CFX_COUNT_REF_H_
 #define CORE_FXCRT_INCLUDE_CFX_COUNT_REF_H_
 
 #include "core/fxcrt/include/cfx_retain_ptr.h"
 #include "core/fxcrt/include/fx_system.h"
 
+// A shared object with Copy on Write semantics that makes it appear as
+// if each one were independent.
 template <class ObjClass>
 class CFX_CountRef {
  public:
   CFX_CountRef() {}
   CFX_CountRef(const CFX_CountRef& other) : m_pObject(other.m_pObject) {}
   ~CFX_CountRef() {}
 
   template <typename... Args>
   ObjClass* Emplace(Args... params) {
     m_pObject.Reset(new CountedObj(params...));
@@ skipping 40 matching lines @@
     }
 
    private:
     intptr_t m_RefCount;
   };
 
   CFX_RetainPtr<CountedObj> m_pObject;
 };
 
 #endif  // CORE_FXCRT_INCLUDE_CFX_COUNT_REF_H_