Provoke VUID-vkDestroyDevice-device-00378 without gfx-rs#3069.

This test should have been included in gfx-rs#3069.

wgpu/tests/encoder.rs

@@ -0,0 +1,11 @@
+use crate::common::{initialize_test, TestParameters};
+
+#[test]
+fn drop_encoder() {
+    initialize_test(TestParameters::default(), |ctx| {
+        let encoder = ctx
+            .device
+            .create_command_encoder(&wgpu::CommandEncoderDescriptor::default());
+        drop(encoder);
+    })
+}

wgpu/tests/root.rs

@@ -5,6 +5,7 @@ mod buffer_copy;
 mod buffer_usages;
 mod clear_texture;
 mod device;
+mod encoder;
 mod example_wgsl;
 mod instance;
 mod poll;