GN: toolchain threading cleanup

tools/gn/ninja_target_writer.h

Index: tools/gn/ninja_target_writer.h
diff --git a/tools/gn/ninja_target_writer.h b/tools/gn/ninja_target_writer.h
index c9c72a77fd1ebd55e274b43d4ca9e014708082b3..e1c3bf8c6ef5e5d8f3acd4a69cbf3e85168ccf61 100644
--- a/tools/gn/ninja_target_writer.h
+++ b/tools/gn/ninja_target_writer.h
@@ -19,7 +19,9 @@ class Target;
 // generated by the NinjaBuildWriter.
 class NinjaTargetWriter {
  public:
-  NinjaTargetWriter(const Target* target, std::ostream& out);
+  NinjaTargetWriter(const Target* target,
+                    const Toolchain* toolchain,
+                    std::ostream& out);
   virtual ~NinjaTargetWriter();
 
   static void RunAndWriteFile(const Target* target);
@@ -27,9 +29,6 @@ class NinjaTargetWriter {
   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
@@ -41,6 +40,7 @@ class NinjaTargetWriter {
 
   const Settings* settings_;  // Non-owning.
   const Target* target_;  // Non-owning.
+  const Toolchain* toolchain_;  // Non-owning.
   std::ostream& out_;
   PathOutput path_output_;