Merge change 6272 into donut

* changes:
  Fix bug 1946195 by making use of the current Locale to set a default value in the language pref list (bug was no selection in the default language list). Fix half of bug 1956707 where speech rate value as read from the settings was translated to a ratio, which applied an improper speech rate on the TTS engine (bug was setting a default rate makes the TTS demo unintelligible). Moved logic to set the default value in the language pref list in a separate private method to improve readability. Changed default rate values so that normal is 1x and the fastest is 2x.