Revert 232657 "GN: toolchain threading cleanup"

trunk/src/tools/gn/ninja_target_writer.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_NINJA_TARGET_WRITER_H_
 #define TOOLS_GN_NINJA_TARGET_WRITER_H_
 
 #include <iosfwd>
 
 #include "base/basictypes.h"
 #include "tools/gn/ninja_helper.h"
 #include "tools/gn/path_output.h"
 
 class FileTemplate;
 class Settings;
 class Target;
 
 // Generates one target's ".ninja" file. The toplevel "build.ninja" file is
 // generated by the NinjaBuildWriter.
 class NinjaTargetWriter {
  public:
-  NinjaTargetWriter(const Target* target,
-                    const Toolchain* toolchain,
-                    std::ostream& out);
+  NinjaTargetWriter(const Target* target, std::ostream& out);
   virtual ~NinjaTargetWriter();
 
   static void RunAndWriteFile(const Target* target);
 
   virtual void Run() = 0;
 
  protected:
+  // Returns the toolchain associated with the target.
+  const Toolchain* GetToolchain() const;
+
   // Returns the string to be appended to source rules that encodes the
   // order-only dependencies for the current target. This will include the
   // "|" character so can just be appended to the source rules. If there are no
   // implicit dependencies, returns the empty string.
   std::string GetSourcesImplicitDeps() const;
 
   // Returns the FileTemplate constructed from the outputs variable.
   FileTemplate GetOutputTemplate() const;
 
   const Settings* settings_;  // Non-owning.
   const Target* target_;  // Non-owning.
-  const Toolchain* toolchain_;  // Non-owning.
   std::ostream& out_;
   PathOutput path_output_;
 
   NinjaHelper helper_;
 
  private:
   void WriteCopyRules();
 
   DISALLOW_COPY_AND_ASSIGN(NinjaTargetWriter);
 };
 
 #endif  // TOOLS_GN_NINJA_TARGET_WRITER_H_