tools/gn: mark first TestTarget parameter as const

tools/gn/test_with_scope.h

 // 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.
 
 #ifndef TOOLS_GN_TEST_WITH_SCOPE_H_
 #define TOOLS_GN_TEST_WITH_SCOPE_H_
 
+#include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "tools/gn/build_settings.h"
 #include "tools/gn/err.h"
 #include "tools/gn/input_file.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scope.h"
 #include "tools/gn/scope_per_file_provider.h"
 #include "tools/gn/settings.h"
 #include "tools/gn/target.h"
 #include "tools/gn/token.h"
 #include "tools/gn/toolchain.h"
 #include "tools/gn/value.h"
 
 // A helper class for setting up a Scope that a test can use. It makes a
 // toolchain and sets up all the build state.
 class TestWithScope {
  public:
   TestWithScope();
   ~TestWithScope();
 
   BuildSettings* build_settings() { return &build_settings_; }
   Settings* settings() { return &settings_; }
+  const Settings* settings() const { return &settings_; }
   Toolchain* toolchain() { return &toolchain_; }
+  const Toolchain* toolchain() const { return &toolchain_; }
   Scope* scope() { return &scope_; }
 
   // This buffer accumulates output from any print() commands executed in the
   // context of this test. Note that the implementation of this is not
   // threadsafe so don't write tests that call print from multiple threads.
   std::string& print_output() { return print_output_; }
 
   // Parse the given string into a label in the default toolchain. This will
   // assert if the label isn't valid (this is intended for hardcoded labels).
   Label ParseLabel(const std::string& str) const;
@@ skipping 51 matching lines @@
   Err parse_err_;
 
   DISALLOW_COPY_AND_ASSIGN(TestParseInput);
 };
 
 // Shortcut for creating targets for tests that take the test setup, a pretty-
 // style label, and a target type and sets everything up. The target will
 // default to public visibility.
 class TestTarget : public Target {
  public:
-  TestTarget(TestWithScope& setup,
+  TestTarget(const TestWithScope& setup,
              const std::string& label_string,
              Target::OutputType type);
   ~TestTarget() override;
 };
 
 #endif  // TOOLS_GN_TEST_WITH_SCOPE_H_