message: [cleanup] Reduce string copies in tree_unwrapper tests.
diff: @@ -168,13 +168,14 @@ struct TreeUnwrapperTestData {
  const char* test_name;
  // The source code for testing must be syntactically correct.
  - std::string source_code;
  + absl::string_view source_code;
  // The reference values and structure of UnwrappedLines to expect.
  ExpectedUnwrappedLineTree expected_unwrapped_lines;
  template <typename... Args>
  - TreeUnwrapperTestData(const char* name, std::string code, Args&&... nodes)
  + TreeUnwrapperTestData(const char* name, absl::string_view code,
  + Args&&... nodes)
  : test_name(name),
  source_code(code),
  expected_unwrapped_lines(ExpectedUnwrappedLine{0},
  @@ -230,7 +231,7 @@ class TreeUnwrapperTest : public ::testing::Test {
  // Takes a string representation of a verilog file and creates a
  // VerilogAnalyzer which holds a concrete syntax tree and token stream view
  // of the file.
  - void MakeTree(const std::string& content) {
  + void MakeTree(absl::string_view content) {
  analyzer_ = absl::make_unique<VerilogAnalyzer>(content, "TEST_FILE");
  verible::util::Status status = ABSL_DIE_IF_NULL(analyzer_)->Analyze();
  EXPECT_OK(status) << "Rejected code: " << std::endl << content;
  @@ -248,7 +249,7 @@ class TreeUnwrapperTest : public ::testing::Test {
  // Creates a TreeUnwrapper populated with a concrete syntax tree and
  // token stream view from the file input
  std::unique_ptr<TreeUnwrapper> CreateTreeUnwrapper(
  - const std::string& source_code) {
  + absl::string_view source_code) {
  MakeTree(source_code);
  const verible::TextStructureView& text_structure_view = analyzer_->Data();
  unwrapper_data_ =
  @@ -271,7 +272,7 @@ class TreeUnwrapperTest : public ::testing::Test {
  // Test that TreeUnwrapper produces the correct UnwrappedLines from an empty
  // file
  TEST_F(TreeUnwrapperTest, UnwrapEmptyFile) {
  - const std::string source_code = "";
  + const absl::string_view source_code = "";
  auto tree_unwrapper = CreateTreeUnwrapper(source_code);
  tree_unwrapper->Unwrap();
  @@ -284,7 +285,7 @@ TEST_F(TreeUnwrapperTest, UnwrapEmptyFile) {
  // Test that TreeUnwrapper produces the correct UnwrappedLines from a blank
  // line.
  TEST_F(TreeUnwrapperTest, UnwrapBlankLineOnly) {
  - const std::string source_code = "\n";
  + const absl::string_view source_code = "\n";
  auto tree_unwrapper = CreateTreeUnwrapper(source_code);
  tree_unwrapper->Unwrap();
  