Merge "replace dlclose() with CloseNativeLibrary() in vulkan layer"

    std::lock_guard<std::mutex> lock(mutex_);

    if (--refcount_ == 0) {

        ALOGV("closing layer library '%s'", path_.c_str());

        dlclose(dlhandle_);

        std::string error_msg;

        if (!android::CloseNativeLibrary(dlhandle_, native_bridge_, &error_msg)) {

            ALOGE("failed to unload library '%s': %s", path_.c_str(), error_msg.c_str());

            refcount_++;

        } else {

           dlhandle_ = nullptr;

        }

    }

}

bool LayerLibrary::EnumerateLayers(size_t library_idx,

                                   std::vector<Layer>& instance_layers) const {