public CallStack addAfter(Call after, Call call) {
        int insertPosition = elements.indexOf(after);
        if (insertPosition < 0) {
            addLast(call);
        } else {
            elements.add(insertPosition + 1, call);
        }
        return this;
    }
Adds an element just after the first occurence of some other element on
the stack. This can not be called during an iteration.

@param after
           the call to add this before. If this call is not present, (the
           same object instance), the new processor is added as the last
           element
@param call
           the call to add
@return this for convenience
docproc/src/main/java/com/yahoo/docproc/CallStack.java