Function cef_string_wide_to_utf8 

pub unsafe extern "C" fn cef_string_wide_to_utf8(
    src: *const wchar_t,
    src_len: usize,
    output: *mut cef_string_utf8_t,
) -> c_int

These functions convert between UTF-8, -16, and -32 strings. They are potentially slow so unnecessary conversions should be avoided. The best possible result will always be written to |output| with the boolean return value indicating whether the conversion is 100% valid.