Remove GN back-compat toolchain args code.

tools/gn/functions.h

 // 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.
 
 #ifndef TOOLS_GN_FUNCTIONS_H_
 #define TOOLS_GN_FUNCTIONS_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 340 matching lines @@
 
 extern const char kToolchain[];
 extern const char kToolchain_HelpShort[];
 extern const char kToolchain_Help[];
 Value RunToolchain(Scope* scope,
                    const FunctionCallNode* function,
                    const std::vector<Value>& args,
                    BlockNode* block,
                    Err* err);
 
-extern const char kToolchainArgs[];
-extern const char kToolchainArgs_HelpShort[];
-extern const char kToolchainArgs_Help[];
-Value RunToolchainArgs(Scope* scope,
-                       const FunctionCallNode* function,
-                       const std::vector<Value>& args,
-                       BlockNode* block,
-                       Err* err);
-
 extern const char kWriteFile[];
 extern const char kWriteFile_HelpShort[];
 extern const char kWriteFile_Help[];
 Value RunWriteFile(Scope* scope,
                    const FunctionCallNode* function,
                    const std::vector<Value>& args,
                    Err* err);
 
 // -----------------------------------------------------------------------------
 
@@ skipping 115 matching lines @@
   Scope* scope_;
   const FunctionCallNode* function_;
   const char* type_description_;
 
   // Set to true when the key is added to the scope so we don't try to
   // delete nonexistant keys which will cause assertions.
   bool key_added_;
 };
 
 #endif  // TOOLS_GN_FUNCTIONS_H_