Add forward_variables_from() and target() to GN

tools/gn/scope_unittest.cc

Index: tools/gn/scope_unittest.cc
diff --git a/tools/gn/scope_unittest.cc b/tools/gn/scope_unittest.cc
index 1dd1e65ca148a317b26f1b7a89754e6268d056fb..ce79973c54edba9e191a5422b5a9b76ca5a471c0 100644
--- a/tools/gn/scope_unittest.cc
+++ b/tools/gn/scope_unittest.cc
@@ -179,13 +179,13 @@ TEST(Scope, NonRecursiveMergeTo) {
     EXPECT_TRUE(err.has_error());
   }
 
-  // Mark used.
+  // Mark dest used.
   {
     Scope new_scope(setup.settings());
 
     Err err;
     Scope::MergeOptions options;
-    options.mark_used = true;
+    options.mark_dest_used = true;
     EXPECT_TRUE(setup.scope()->NonRecursiveMergeTo(
         &new_scope, options, &assignment, "error", &err));
     EXPECT_FALSE(err.has_error());