message: Fix `fname` argument for `GetFileSystemForFile()`
diff: @@ -100,7 +100,7 @@ class ModularFileSystemTest : public ::testing::TestWithParam<std::string> {
  void SetUp() override {
  FileSystem* fs = nullptr;
  - Status s = env_->GetFileSystemForFile(GetParam(), &fs);
  + Status s = env_->GetFileSystemForFile(root_dir_, &fs);
  if (fs == nullptr || !s.ok())
  GTEST_SKIP() << "No filesystem registered: " << s;
  