code: function updateInputCursor() {
              if (isValidInput) {
                var inputLength = input[0].value.length;
  
                try {
                  input[0].selectionStart = input[0].selectionEnd = inputLength;
                } catch (e) {
                  // Chrome does not allow setting a selection for number inputs and just throws
                  // a DOMException as soon as something tries to set a selection programmatically.
                  // Faking the selection properties for the ChipsController works for our tests.
                  var selectionDescriptor = { writable: true, value: inputLength };
                  Object.defineProperty(input[0], 'selectionStart', selectionDescriptor);
                  Object.defineProperty(input[0], 'selectionEnd', selectionDescriptor);
                }
              }
            }
docs: Updates the cursor position of the input.
  This is necessary to test the cursor position.