function offsetInToken(ctx) {
        var offset = ctx.pos.ch - ctx.token.start;
        if (offset < 0) {
            console.log("CodeHintUtils: _offsetInToken - Invalid context: pos not in the current token!");
        }
        return offset;
    }
In the given context, get the character offset of pos from the start of the token.
@param {!{editor:!CodeMirror, pos:!{ch:number, line:number}, token:Object}} context
@return {number}