Introduce a separate API for retrieving locale set from the host environment
used for regional preferences localization.
MozReview-Commit-ID: 3597QstZjS3
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extra : rebase_source : 2ac30ba2f2c9bd1ed308cfe7be88f6add4f0f5ae
Since we have to keep --with-intl-api=no setting, we allow OSPrefrences API wiout ENABLE_INTL_API.
MozReview-Commit-ID: 8sQHW6iq9Ss
--HG--
extra : rebase_source : 94e2efbeeb70f3edc519ffc9bfeaf7416ea1dc0e