Replicate to all renderers the accepted languages set by a layout test.

components/test_runner/tracked_dictionary.cc

 // Copyright 2016 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 "components/test_runner/tracked_dictionary.h"
 
 #include <utility>
 
 namespace test_runner {
 
@@ skipping 23 matching lines @@
   }
 
   changed_values_.Set(path, new_value->CreateDeepCopy());
   current_values_.Set(path, std::move(new_value));
 }
 
 void TrackedDictionary::SetBoolean(const std::string& path, bool new_value) {
   Set(path, make_scoped_ptr(new base::FundamentalValue(new_value)));
 }
 
+void TrackedDictionary::SetString(const std::string& path,
+                                  const std::string& new_value) {
+  Set(path, make_scoped_ptr(new base::StringValue(new_value)));
+}
+
 }  // namespace test_runner