Implement tracking of BUILD.gn files used to define target, toolchain or

tools/gn/loader.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/loader.h"
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "tools/gn/build_settings.h"
@@ skipping 233 matching lines @@
         FROM_HERE, base::Bind(&LoaderImpl::DecrementPendingLoads, this));
     return;
   }
 
   if (g_scheduler->verbose_logging()) {
     g_scheduler->Log("Running", file_name.value() + " with toolchain " +
                      settings->toolchain_label().GetUserVisibleName(false));
   }
 
   Scope our_scope(settings->base_config());
+  our_scope.AddSourceFile(file_name);
   ScopePerFileProvider per_file_provider(&our_scope, true);
   our_scope.set_source_dir(file_name.GetDir());
 
   // Targets, etc. generated as part of running this file will end up here.
   Scope::ItemVector collected_items;
   our_scope.set_item_collector(&collected_items);
 
   ScopedTrace trace(TraceItem::TRACE_FILE_EXECUTE, file_name.value());
   trace.SetToolchain(settings->toolchain_label());
 
@@ skipping 157 matching lines @@
     const SourceFile& file_name,
     const base::Callback<void(const ParseNode*)>& callback,
     Err* err) {
   if (async_load_file_.is_null()) {
     return g_scheduler->input_file_manager()->AsyncLoadFile(
         origin, build_settings, file_name, callback, err);
   }
   return async_load_file_.Run(
       origin, build_settings, file_name, callback, err);
 }