Implement initCopySurfaceDstDesc for Vulkan

src/gpu/vk/GrVkGpu.h

Index: src/gpu/vk/GrVkGpu.h
diff --git a/src/gpu/vk/GrVkGpu.h b/src/gpu/vk/GrVkGpu.h
index 91f9d4d3791c39da47951e5aca89f9f116e6f174..5872f18671972415e5d595472fa51b57f1e0c9ad 100644
--- a/src/gpu/vk/GrVkGpu.h
+++ b/src/gpu/vk/GrVkGpu.h
@@ -75,9 +75,7 @@ public:
                                int* effectiveSampleCnt,
                                SkAutoTDeleteArray<SkPoint>*);
 
-    bool initCopySurfaceDstDesc(const GrSurface* src, GrSurfaceDesc* desc) const override {
-        return false;
-    }
+    bool initCopySurfaceDstDesc(const GrSurface* src, GrSurfaceDesc* desc) const override;
 
     void xferBarrier(GrRenderTarget*, GrXferBarrierType) override {}