Replace `unimpl` comments with `= delete`.

A handful of `unimpl`ed copy constructors were actually supplied as
{} instead of being left unimplemented, but they were not actually used.

Change-Id: I9b88173aeb0cc87f793ee40dfba1b5e5a06d7497
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/308565
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
diff --git a/src/gpu/GrResourceProviderPriv.h b/src/gpu/GrResourceProviderPriv.h
index a440f95..feeca34 100644
--- a/src/gpu/GrResourceProviderPriv.h
+++ b/src/gpu/GrResourceProviderPriv.h
@@ -19,8 +19,8 @@
 
 private:
     explicit GrResourceProviderPriv(GrResourceProvider* provider) : fResourceProvider(provider) {}
-    GrResourceProviderPriv(const GrResourceProviderPriv&); // unimpl
-    GrResourceProviderPriv& operator=(const GrResourceProviderPriv&); // unimpl
+    GrResourceProviderPriv(const GrResourceProviderPriv&) = delete;
+    GrResourceProviderPriv& operator=(const GrResourceProviderPriv&) = delete;
 
     // No taking addresses of this type.
     const GrResourceProviderPriv* operator&() const;