static/ext/src/ux/form/field/ClearButton.js
function() {
            if (!this.isTextArea) {
                return false;
            }

            var inputEl = this.textField.inputEl;
            var overflowY = inputEl.getStyle('overflow-y');
            if (overflowY == 'hidden' || overflowY == 'visible') {
                return false;
            }
            if (overflowY == 'scroll') {
                return true;
            }
            //noinspection RedundantIfStatementJS
            if (inputEl.dom.scrollHeight <= inputEl.dom.clientHeight) {
                return false;
            }
            return true;
        }
function() {
            if (!this.isTextArea) {
                return false;
            }

            var inputEl = this.textField.inputEl;
            var overflowY = inputEl.getStyle('overflow-y');
            if (overflowY == 'hidden' || overflowY == 'visible') {
                return false;
            }
            if (overflowY == 'scroll') {
                return true;
            }
            //noinspection RedundantIfStatementJS
            if (inputEl.dom.scrollHeight <= inputEl.dom.clientHeight) {
                return false;
            }
            return true;
        }
Checks if the field we are attached to currently has a scrollbar