message: fix dropdown style when input is shown
diff: @@ -310,7 +310,7 @@ export default class Dropdown extends React.Component {
  // Note the menu sits inside the AccessibleButton div so it's anchored
  // to the input, but overflows below it. The root contains both.
  return <div className={classnames(dropdownClasses)} ref={this._collectRoot}>
  - <AccessibleButton className="mx_Dropdown_input" onClick={this._onInputClick}>
  + <AccessibleButton className="mx_Dropdown_input mx_no_textinput" onClick={this._onInputClick}>
  { currentValue }
  <span className="mx_Dropdown_arrow"></span>
  { menu }
  