Fix SkVerticesPriv on MSVC 2017

Change-Id: I1ce2d98de0f3640ae9ccbae5b2a601bf70a35423
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/280756
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
diff --git a/src/core/SkVerticesPriv.h b/src/core/SkVerticesPriv.h
index 81edc28..e296ff6 100644
--- a/src/core/SkVerticesPriv.h
+++ b/src/core/SkVerticesPriv.h
@@ -38,7 +38,8 @@
 
 private:
     explicit SkVerticesPriv(SkVertices* vertices) : fVertices(vertices) {}
-    SkVerticesPriv(const SkVerticesPriv&) = delete;
+    // Never called due to RVO in priv(), but must exist for MSVC 2017.
+    SkVerticesPriv(const SkVerticesPriv&) = default;
     SkVerticesPriv& operator=(const SkVerticesPriv&) = delete;
 
     // No taking addresses of this type