GN: toolchain threading cleanup

tools/gn/input_conversion.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 "input_conversion.h"
 
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "tools/gn/build_settings.h"
 #include "tools/gn/err.h"
@@ skipping 99 matching lines @@
     return Value();
 
   // The result should either be a list or a literal, anything else is
   // invalid.
   if (!expression->AsList() && !expression->AsLiteral()) {
     *err = MakeParseErr(input, origin, Err());
     return Value();
   }
 
   BuildSettings build_settings;
-  Label empty_label;
-  Toolchain toolchain(empty_label);
-  Settings settings(&build_settings, &toolchain, std::string());
+  Settings settings(&build_settings, std::string());
   Scope scope(&settings);
 
   Err nested_err;
   Value result = expression->Execute(&scope, &nested_err);
   if (nested_err.has_error()) {
     *err = MakeParseErr(input, origin, nested_err);
     return Value();
   }
 
   // The returned value will have references to the temporary parse nodes we
@@ skipping 63 matching lines @@
     return ParseString(input, origin, err);
   if (input_conversion == "string")
     return Value(origin, input);
   if (input_conversion == "list lines")
     return ParseList(input, origin, err);
 
   *err = Err(input_conversion_value, "Not a valid read file mode.",
              "Have you considered a career in retail?");
   return Value();
 }