Add automatic generation of mipmaps to Vulkan

src/gpu/vk/GrVkImageView.h

 /*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #ifndef GrVkImageView_DEFINED
 #define GrVkImageView_DEFINED
 
 #include "GrTypes.h"
 
 #include "GrVkResource.h"
 
 #include "vk/GrVkDefines.h"
 
 class GrVkImageView : public GrVkResource {
 public:
     enum Type {
         kColor_Type,
         kStencil_Type
     };
 
-    static const GrVkImageView* Create(GrVkGpu* gpu, VkImage image, VkFormat format, Type viewType);
+    static const GrVkImageView* Create(const GrVkGpu* gpu, VkImage image, VkFormat format, 
+                                       Type viewType, uint32_t miplevels);
 
     VkImageView imageView() const { return fImageView; }
 
 private:
     GrVkImageView(VkImageView imageView) : INHERITED(), fImageView(imageView) {}
 
     GrVkImageView(const GrVkImageView&);
     GrVkImageView& operator=(const GrVkImageView&);
 
     void freeGPUData(const GrVkGpu* gpu) const override;
 
     VkImageView  fImageView;
 
     typedef GrVkResource INHERITED;
 };
 
 #endif