Allow GN configs to have sub-configs.

tools/gn/builder.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_BUILDER_H_
 #define TOOLS_GN_BUILDER_H_
 
 #include "base/callback.h"
 #include "base/containers/hash_tables.h"
 #include "base/macros.h"
@@ skipping 40 matching lines @@
 
   // If there are any undefined references, returns false and sets the error.
   bool CheckForBadItems(Err* err) const;
 
  private:
   friend class base::RefCountedThreadSafe<Builder>;
 
   virtual ~Builder();
 
   bool TargetDefined(BuilderRecord* record, Err* err);
+  bool ConfigDefined(BuilderRecord* record, Err* err);
   bool ToolchainDefined(BuilderRecord* record, Err* err);
 
   // Returns the record associated with the given label. This function checks
   // that if we already have references for it, the type matches. If no record
   // exists yet, a new one will be created.
   //
   // If any of the conditions fail, the return value will be null and the error
   // will be set. request_from is used as the source of the error.
   BuilderRecord* GetOrCreateRecordOfType(const Label& label,
                                          const ParseNode* request_from,
@@ skipping 61 matching lines @@
   // Owning pointers.
   typedef base::hash_map<Label, BuilderRecord*> RecordMap;
   RecordMap records_;
 
   ResolvedCallback resolved_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(Builder);
 };
 
 #endif  // TOOLS_GN_BUILDER_H_