Use single DestroyObject command in the wire

Bug: dawn:83
Change-Id: Ic875d5111f59e7166d2decb3dc6a84973d9babdf
Reviewed-on: https://dawn-review.googlesource.com/c/3680
Commit-Queue: Austin Eng <enga@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

src/dawn_wire/WireCmd.h

@@ -71,6 +71,13 @@ namespace dawn_wire {
         uint32_t dataLength;
     };
 
+    struct DestroyObjectCmd {
+        WireCmd commandId = WireCmd::DestroyObject;
+
+        ObjectType objectType;
+        ObjectId objectId;
+    };
+
 }  // namespace dawn_wire
 
 #endif  // DAWNWIRE_WIRECMD_H_