GN threading refactor

tools/gn/function_set_default_toolchain.cc

 // 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.
 
 #include "tools/gn/build_settings.h"
 #include "tools/gn/functions.h"
+#include "tools/gn/loader.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scope.h"
 #include "tools/gn/settings.h"
-#include "tools/gn/toolchain_manager.h"
 
 namespace functions {
 
 const char kSetDefaultToolchain[] = "set_default_toolchain";
 const char kSetDefaultToolchain_Help[] =
     "set_default_toolchain: Sets the default toolchain name.\n"
     "\n"
     "  set_default_toolchain(toolchain_label)\n"
     "\n"
     "  The given label should identify a toolchain definition (see\n"
@@ skipping 24 matching lines @@
                              const FunctionCallNode* function,
                              const std::vector<Value>& args,
                              Err* err) {
   if (!scope->IsProcessingBuildConfig()) {
     *err = Err(function->function(), "Must be called from build config.",
         "set_default_toolchain can only be called from the build configuration "
         "file.");
     return Value();
   }
 
-  // Ignore non-default-build-config invocations.
-  if (!scope->IsProcessingDefaultBuildConfig())
+  // When the loader is expecting the default toolchain to be set, it will set
+  // this key on the scope to point to the destination.
+  Label* default_toolchain_dest = static_cast<Label*>(
+      scope->GetProperty(Loader::kDefaultToolchainKey, NULL));
+  if (!default_toolchain_dest)
     return Value();
 
   const SourceDir& current_dir = scope->GetSourceDir();
   const Label& default_toolchain = ToolchainLabelForScope(scope);
 
   if (!EnsureSingleStringArg(function, args, err))
     return Value();
   Label toolchain_label(
       Label::Resolve(current_dir, default_toolchain, args[0], err));
   if (toolchain_label.is_null())
     return Value();
 
-  ToolchainManager& mgr =
-      scope->settings()->build_settings()->toolchain_manager();
-  mgr.SetDefaultToolchainUnlocked(toolchain_label, function->GetRange(), err);
+  *default_toolchain_dest = toolchain_label;
   return Value();
 }
 
 }  // namespace functions