Make GrVkStencilAttachment derive form GrVkImage

src/gpu/vk/GrVkStencilAttachment.h

 /*
 * Copyright 2015 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #ifndef GrVkStencil_DEFINED
 #define GrVkStencil_DEFINED
 
 #include "GrStencilAttachment.h"
 #include "GrVkImage.h"
 #include "vulkan/vulkan.h"
 
 class GrVkImageView;
 class GrVkGpu;
 
-class GrVkStencilAttachment : public GrStencilAttachment {
+class GrVkStencilAttachment : public GrStencilAttachment, public GrVkImage {
 public:
     struct Format {
         VkFormat  fInternalFormat;
         int  fStencilBits;
         int  fTotalBits;
         bool fPacked;
     };
 
     static GrVkStencilAttachment* Create(GrVkGpu* gpu, GrGpuResource::LifeCycle lifeCycle,
                                          int width, int height,
                                          int sampleCnt, const Format& format);
 
     ~GrVkStencilAttachment() override;
 
-    const GrVkImage::Resource* imageResource() const { return fImageResource;  }
+    const GrVkImage::Resource* imageResource() const { return this->resource(); }
     const GrVkImageView* stencilView() const { return fStencilView; }
 
     VkFormat vkFormat() const { return fFormat.fInternalFormat; }
 
 protected:
     void onRelease() override;
     void onAbandon() override;
 
 private:
     size_t onGpuMemorySize() const override;
 
     GrVkStencilAttachment(GrVkGpu* gpu,
                           GrGpuResource::LifeCycle lifeCycle,
                           const Format& format,
                           const GrVkImage::ImageDesc&,
                           const GrVkImage::Resource*,
                           const GrVkImageView* stencilView);
 
     GrVkGpu* getVkGpu() const;
 
     Format fFormat;
 
-    const GrVkImage::Resource* fImageResource;
     const GrVkImageView*       fStencilView;
-
-    typedef GrStencilAttachment INHERITED;
 };
 
 #endif