Bug 40199: Avoid using system locale for intl.accept_languages in GeckoView

  private String computeAcceptLanguages() {

    final ArrayList<String> locales = new ArrayList<String>();

    // Explicitly-set app prefs come first:

    if (mRequestedLocales != null) {

      for (final String locale : mRequestedLocales) {

        locales.add(locale.toLowerCase(Locale.ROOT));

    // In Desktop, these are defined in the `intl.accept_languages` localized property.

    // At some point we should probably use the same values here, but for now we use a simple

    // strategy which will hopefully result in reasonable acceptLanguage values.

    if (mRequestedLocales != null && mRequestedLocales.length > 0) {

      String locale = mRequestedLocales[0].toLowerCase(Locale.ROOT);

      // No need to include `en-us` twice.

      if (!locale.equals("en-us")) {

        locales.add(locale);

        if (locale.contains("-")) {

          String lang = locale.split("-")[0];

          // No need to include `en` twice.

          if (!lang.equals("en")) {

            locales.add(lang);

          }

        }

    // OS prefs come second:

    for (final String locale : getDefaultLocales()) {

      final String localeLowerCase = locale.toLowerCase(Locale.ROOT);

      if (!locales.contains(localeLowerCase)) {

        locales.add(localeLowerCase);

      }

    }

    locales.add("en-us");

    locales.add("en");

    return TextUtils.join(",", locales);

  }