Fix BCP47 language tag validation - extlang and privateuse extension
Extlang subtag can only be preceded by 2 or 3 letter language code.
The length check for the preceding subtag was missing.
In addition, the singleton check for private use extension was buggy.
Add 'USE_CHROMIUM_ICU" to BUILD.gn to let v8 take different code paths
depending on whether or not Chromium's ICU with patches is used. This
distinction can be important for Node.js
Test: v8: test262/intl402/Intl/getCanonicalLocales/*
Reviewed-by: Jungshik Shin <firstname.lastname@example.org>
4 files changed