Add forward_variables_from() and target() to GN

tools/gn/test_with_scope.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/test_with_scope.h"
 
 #include "base/bind.h"
 #include "tools/gn/parser.h"
 #include "tools/gn/tokenizer.h"
 
 TestWithScope::TestWithScope()
     : build_settings_(),
       settings_(&build_settings_, std::string()),
       toolchain_(&settings_, Label(SourceDir("//toolchain/"), "default")),
-      scope_(&settings_) {
+      scope_(&settings_),
+      scope_progammatic_provider_(&scope_, true) {
   build_settings_.SetBuildDir(SourceDir("//out/Debug/"));
   build_settings_.set_print_callback(
       base::Bind(&TestWithScope::AppendPrintOutput, base::Unretained(this)));
 
   settings_.set_toolchain_label(toolchain_.label());
   settings_.set_default_toolchain_label(toolchain_.label());
 
   SetupToolchain(&toolchain_);
 }
 
@@ skipping 123 matching lines @@
                        const std::string& label_string,
                        Target::OutputType type)
     : Target(setup.settings(), setup.ParseLabel(label_string)) {
   visibility().SetPublic();
   set_output_type(type);
   SetToolchain(setup.toolchain());
 }
 
 TestTarget::~TestTarget() {
 }