GN threading refactor

tools/gn/build_settings.cc

Index: tools/gn/build_settings.cc
diff --git a/tools/gn/build_settings.cc b/tools/gn/build_settings.cc
index 0a75569b1dbbf7211e61d6eef63ef30ac4533e50..7d1bcf0b2c9624169d358a193235507d9ed5531e 100644
--- a/tools/gn/build_settings.cc
+++ b/tools/gn/build_settings.cc
@@ -7,27 +7,18 @@
 #include "base/file_util.h"
 #include "tools/gn/filesystem_utils.h"
 
-BuildSettings::BuildSettings()
-    : using_external_generator_(false),
-      item_tree_(),
-      target_manager_(this),
-      toolchain_manager_(this) {
+BuildSettings::BuildSettings() {
 }
 
 BuildSettings::BuildSettings(const BuildSettings& other)
     : root_path_(other.root_path_),
       root_path_utf8_(other.root_path_utf8_),
       secondary_source_path_(other.secondary_source_path_),
-      using_external_generator_(other.using_external_generator_),
       python_path_(other.python_path_),
       build_config_file_(other.build_config_file_),
       build_dir_(other.build_dir_),
       build_to_source_dir_string_(other.build_to_source_dir_string_),
-      build_args_(other.build_args_),
-      target_resolved_callback_(),  // Don't copy.
-      item_tree_(),
-      target_manager_(this),
-      toolchain_manager_(this) {
+      build_args_(other.build_args_) {
 }
 
 BuildSettings::~BuildSettings() {
@@ -66,3 +57,8 @@ base::FilePath BuildSettings::GetFullPathSecondary(
   return dir.Resolve(secondary_source_path_);
 }
 
+void BuildSettings::ItemDefined(scoped_ptr<Item> item) const {
+  DCHECK(item);
+  if (!item_defined_callback_.is_null())
+    item_defined_callback_.Run(item.Pass());
+}