Add not_needed function

tools/gn/function_template.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/functions.h"
 
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scope.h"
 #include "tools/gn/template.h"
 #include "tools/gn/value.h"
@@ skipping 187 matching lines @@
   // The "right" thing to do would be to walk the syntax tree inside the
   // template, find all identifier references, and mark those variables used.
   // This is annoying and error-prone to implement and takes extra time to run
   // for this narrow use case.
   //
   // Templates are most often defined in .gni files which don't get
   // used-variable checking anyway, and this case is annoying enough that the
   // incremental value of unused variable checking isn't worth the
   // alternatives. So all values in scope before this template definition are
   // exempted from unused variable checking.
-  scope->MarkAllUsed();
+  scope->MarkAllUsed(err);
 
   return Value();
 }
 
 }  // namespace functions