Make `gn refs` look at script files.

tools/gn/command_refs.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 <stddef.h>
 
 #include <map>
 #include <set>
 
 #include "base/command_line.h"
@@ skipping 127 matching lines @@
   }
   for (const auto& cur_file : target->inputs()) {
     if (cur_file == file)
       return true;
   }
   for (const auto& cur_file : target->data()) {
     if (cur_file == file.value())
       return true;
   }
 
+  if (target->action_values().script().value() == file.value())
+    return true;
+
   std::vector<SourceFile> outputs;
   target->action_values().GetOutputsAsSourceFiles(target, &outputs);
   for (const auto& cur_file : outputs) {
     if (cur_file == file)
       return true;
   }
   return false;
 }
 
 void GetTargetsContainingFile(Setup* setup,
@@ skipping 316 matching lines @@
 
   // If you ask for the references of a valid target, but that target has
   // nothing referencing it, we'll get here without having printed anything.
   if (!quiet && cnt == 0)
     OutputString("Nothing references this.\n", DECORATION_YELLOW);
 
   return 0;
 }
 
 }  // namespace commands