Allow creation and modification of scopes in GN.

tools/gn/visibility_unittest.cc

 // Copyright 2014 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 "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/err.h"
 #include "tools/gn/label.h"
+#include "tools/gn/scope.h"
 #include "tools/gn/value.h"
 #include "tools/gn/visibility.h"
 
 TEST(Visibility, CanSeeMe) {
   Value list(nullptr, Value::LIST);
   list.list_value().push_back(Value(nullptr, "//rec/*"));    // Recursive.
   list.list_value().push_back(Value(nullptr, "//dir:*"));    // One dir.
   list.list_value().push_back(Value(nullptr, "//my:name"));  // Exact match.
 
   Err err;
@@ skipping 25 matching lines @@
 }
 
 TEST(Visibility, Private) {
   Err err;
   Visibility vis;
   ASSERT_TRUE(vis.Set(SourceDir("//"), Value(nullptr, Value::LIST), &err));
 
   EXPECT_FALSE(vis.CanSeeMe(Label(SourceDir("//random/"), "thing")));
   EXPECT_FALSE(vis.CanSeeMe(Label(SourceDir("//"), "")));
 }