GN: toolchain threading cleanup

tools/gn/settings.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_SETTINGS_H_
 #define TOOLS_GN_SETTINGS_H_
 
 #include "base/files/file_path.h"
 #include "tools/gn/build_settings.h"
 #include "tools/gn/import_manager.h"
@@ skipping 20 matching lines @@
     LINUX,
     MAC,
     WIN
   };
 
   // Constructs a toolchain settings. The output_subdir_name is the name we
   // should use for the subdirectory in the build output directory for this
   // toolchain's outputs. It should have no slashes in it. The default
   // toolchain should use an empty string.
   Settings(const BuildSettings* build_settings,
-           const Toolchain* toolchain,
            const std::string& output_subdir_name);
   ~Settings();
 
   const BuildSettings* build_settings() const { return build_settings_; }
 
-  // Danger: this must only be used for getting the toolchain label until the
-  // toolchain has been resolved. Otherwise, it will be modified on an
-  // arbitrary thread when the toolchain invocation is found. Generally, you
-  // will only read this from the target generation where we know everything
-  // has been resolved and won't change.
-  const Toolchain* toolchain() const { return toolchain_; }
+  const Label& toolchain_label() const { return toolchain_label_; }
+  void set_toolchain_label(const Label& l) { toolchain_label_ = l; }
+
+  // Indicates if this corresponds to the default toolchain.
+  bool is_default() const { return is_default_; }
+  void set_is_default(bool id) { is_default_ = id; }
 
   bool IsMac() const { return target_os_ == MAC; }
   bool IsLinux() const { return target_os_ == LINUX; }
   bool IsWin() const { return target_os_ == WIN; }
 
   TargetOS target_os() const { return target_os_; }
   void set_target_os(TargetOS t) { target_os_ = t; }
 
   const OutputFile& toolchain_output_subdir() const {
     return toolchain_output_subdir_;
@@ skipping 24 matching lines @@
   bool greedy_target_generation() const {
     return greedy_target_generation_;
   }
   void set_greedy_target_generation(bool gtg) {
     greedy_target_generation_ = gtg;
   }
 
  private:
   const BuildSettings* build_settings_;
 
-  const Toolchain* toolchain_;
+  Label toolchain_label_;
+  bool is_default_;
 
   TargetOS target_os_;
 
   mutable ImportManager import_manager_;
 
   // The subdirectory inside the build output for this toolchain. For the
   // default toolchain, this will be empty (since the deafult toolchain's
   // output directory is the same as the build directory). When nonempty, this
   // is guaranteed to end in a slash.
   OutputFile toolchain_output_subdir_;
 
   // Full source file path to the toolchain output directory.
   SourceDir toolchain_output_dir_;
 
   SourceDir toolchain_gen_dir_;
 
   Scope base_config_;
 
   bool greedy_target_generation_;
 
   DISALLOW_COPY_AND_ASSIGN(Settings);
 };
 
 #endif  // TOOLS_GN_SETTINGS_H_