Function cef_string_ascii_to_wide 

pub unsafe extern "C" fn cef_string_ascii_to_wide(
    src: *const c_char,
    src_len: usize,
    output: *mut cef_string_wide_t,
) -> c_int

These functions convert an ASCII string, typically a hardcoded constant, to a Wide/UTF16 string. Use instead of the UTF8 conversion routines if you know the string is ASCII.