Add get_target_outputs function to GN

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/message_loop/message_loop.h"
 #include "base/stl_util.h"
 #include "tools/gn/build_settings.h"
@@ skipping 229 matching lines @@
 
   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());
   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());
 
   Err err;
   root->Execute(&our_scope, &err);
   if (err.has_error())
     g_scheduler->FailWithError(err);
 
+  // Pass all of the items that were defined off to the builder.
+  for (size_t i = 0; i < collected_items.size(); i++)
+    settings->build_settings()->ItemDefined(collected_items[i]->Pass());
+
   trace.Done();
 
   main_loop_->PostTask(FROM_HERE, base::Bind(&LoaderImpl::DidLoadFile, this));
 }
 
 void LoaderImpl::BackgroundLoadBuildConfig(
     Settings* settings,
     const Scope::KeyValueMap& toolchain_overrides,
     const ParseNode* root) {
   if (!root) {
@@ skipping 124 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);
 }