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

components/test_runner/tracked_dictionary.h

Index: components/test_runner/tracked_dictionary.h
diff --git a/components/test_runner/tracked_dictionary.h b/components/test_runner/tracked_dictionary.h
index c29eeb51661362e7704a013eae97f6e7566de199..7b7182da75f108aef7573206e47abf1d03d1a33d 100644
--- a/components/test_runner/tracked_dictionary.h
+++ b/components/test_runner/tracked_dictionary.h
@@ -44,6 +44,7 @@ class TEST_RUNNER_EXPORT TrackedDictionary {
 
   // Type-specific setter for convenience.
   void SetBoolean(const std::string& path, bool new_value);
+  void SetString(const std::string& path, const std::string& new_value);
 
  private:
   base::DictionaryValue current_values_;