GN: Use std::unique_ptr in Loader::ToolchainRecordMap.

tools/gn/loader.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_LOADER_H_
 #define TOOLS_GN_LOADER_H_
 
 #include <map>
+#include <memory>
 #include <set>
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "tools/gn/label.h"
 #include "tools/gn/scope.h"
 
 namespace base {
 class MessageLoop;
 }
@@ skipping 147 matching lines @@
   // mocking purposes.
   AsyncLoadFileCallback async_load_file_;
 
   typedef std::set<LoadID> LoadIDSet;
   LoadIDSet invocations_;
 
   const BuildSettings* build_settings_;
   Label default_toolchain_label_;
 
   // Records for the build config file loads.
-  // Owning pointers.
-  typedef std::map<Label, ToolchainRecord*> ToolchainRecordMap;
+  typedef std::map<Label, std::unique_ptr<ToolchainRecord>> ToolchainRecordMap;
   ToolchainRecordMap toolchain_records_;
 };
 
 #endif  // TOOLS_GN_LOADER_H_