function normalizeSubPixelRoundingRule(value) {
    if (isSubPixelRoundingRuleUnknown(value)) {
        return DEFAULT_SUBPIXEL_ROUNDING_RULE;
    }
    return value;
}
Ensures the returned value is always a valid subpixel rounding enum value,
defaulting to {@link SUBPIXEL_ROUNDING_OCCURRENCES.NEVER} if input is missing or invalid.
@private
@param {SUBPIXEL_ROUNDING_OCCURRENCES} value - The subpixel rounding enum value to normalize.
@returns {SUBPIXEL_ROUNDING_OCCURRENCES} Returns a valid subpixel rounding enum value.