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..92f4a667c1a399d544a43e3e3a38eba2bad33600 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(GrVkGpu* gpu);
+
 protected:
     GrVkTexture(GrVkGpu*, const GrSurfaceDesc&,
                 const GrVkImage::Resource*, const GrVkImageView* imageView);