Implement tracking of BUILD.gn files used to define target, toolchain or

tools/gn/test_with_scope.cc

Index: tools/gn/test_with_scope.cc
diff --git a/tools/gn/test_with_scope.cc b/tools/gn/test_with_scope.cc
index b239c640052da0610105d89e6b70df623be44860..09ac33c3c0509ecc985fd32dd001870badd16838 100644
--- a/tools/gn/test_with_scope.cc
+++ b/tools/gn/test_with_scope.cc
@@ -23,8 +23,8 @@ BuildSettings CreateBuildSettingsForTest() {
 TestWithScope::TestWithScope()
     : build_settings_(CreateBuildSettingsForTest()),
       settings_(&build_settings_, std::string()),
-      toolchain_(&settings_, Label(SourceDir("//toolchain/"), "default")),
-      scope_(&settings_),
+      toolchain_(&settings_, Label(SourceDir("//toolchain/"), "default"), {}),
+      scope_(&settings_, {}),
       scope_progammatic_provider_(&scope_, true) {
   build_settings_.set_print_callback(
       base::Bind(&TestWithScope::AppendPrintOutput, base::Unretained(this)));
@@ -214,7 +214,7 @@ TestParseInput::~TestParseInput() {
 TestTarget::TestTarget(const TestWithScope& setup,
                        const std::string& label_string,
                        Target::OutputType type)
-    : Target(setup.settings(), setup.ParseLabel(label_string)) {
+    : Target(setup.settings(), setup.ParseLabel(label_string), {}) {
   visibility().SetPublic();
   set_output_type(type);
   SetToolchain(setup.toolchain());