Add automatic generation of mipmaps to Vulkan

src/gpu/vk/GrVkTexture.h

Index: src/gpu/vk/GrVkTexture.h
diff --git a/src/gpu/vk/GrVkTexture.h b/src/gpu/vk/GrVkTexture.h
index 936eeb7b30efb30f0768509ba058dcae73f2a133..a5e82e866c42d462c0712cf88473a089d0ccb92e 100644
--- a/src/gpu/vk/GrVkTexture.h
+++ b/src/gpu/vk/GrVkTexture.h
@@ -33,6 +33,8 @@ public:
 
     const GrVkImageView* textureView() const { return fTextureView; }
 
+    bool reallocForMipmap(const GrVkGpu* gpu);
+
 protected:
     GrVkTexture(GrVkGpu*, const GrSurfaceDesc&,
                 const GrVkImage::Resource*, const GrVkImageView* imageView);