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

tools/gn/operators_unittest.cc

Index: tools/gn/operators_unittest.cc
diff --git a/tools/gn/operators_unittest.cc b/tools/gn/operators_unittest.cc
index 4c9c670a133d514cfa2d01f5da5a87f12147bc64..84c31283aae3a294c3bef79aaf7199284069a7fe 100644
--- a/tools/gn/operators_unittest.cc
+++ b/tools/gn/operators_unittest.cc
@@ -336,8 +336,8 @@ TEST(Operators, NonemptyOverwriting) {
 
   // Set up "foo" with a nonempty scope.
   const char bar[] = "bar";
-  old_value = Value(
-      nullptr, std::unique_ptr<Scope>(new Scope(setup.settings())));
+  old_value =
+      Value(nullptr, std::unique_ptr<Scope>(new Scope(setup.settings(), {})));
   old_value.scope_value()->SetValue(bar, Value(nullptr, "bar"), nullptr);
   setup.scope()->SetValue(foo, old_value, nullptr);
 
@@ -350,7 +350,7 @@ TEST(Operators, NonemptyOverwriting) {
 
   // Assigning an empty list should succeed.
   node.SetRightToValue(
-      Value(nullptr, std::unique_ptr<Scope>(new Scope(setup.settings()))));
+      Value(nullptr, std::unique_ptr<Scope>(new Scope(setup.settings(), {}))));
   node.Execute(setup.scope(), &err);
   ASSERT_FALSE(err.has_error());
   new_value = setup.scope()->GetValue(foo);