Create GrVkCopyPipeline class

This creates a special subclass of GrVkPipeline that we can use for doing
copies on draws. Currently this is not hooked into the system.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2353563003

Review-Url: https://codereview.chromium.org/2353563003
diff --git a/src/gpu/vk/GrVkPipeline.h b/src/gpu/vk/GrVkPipeline.h
index bec4aeb..2565185 100644
--- a/src/gpu/vk/GrVkPipeline.h
+++ b/src/gpu/vk/GrVkPipeline.h
@@ -43,16 +43,14 @@
     }
 #endif
 
-private:
+protected:
     GrVkPipeline(VkPipeline pipeline) : INHERITED(), fPipeline(pipeline) {}
 
-    GrVkPipeline(const GrVkPipeline&);
-    GrVkPipeline& operator=(const GrVkPipeline&);
-
-    void freeGPUData(const GrVkGpu* gpu) const override;
-
     VkPipeline  fPipeline;
 
+private:
+    void freeGPUData(const GrVkGpu* gpu) const override;
+
     typedef GrVkResource INHERITED;
 };