message: warn on unload when uploading file(s)
diff: @@ -271,6 +271,7 @@ module.exports = React.createClass({
  this._updateConfCallNotification();
  + window.addEventListener('beforeunload', this.onPageUnload);
  window.addEventListener('resize', this.onResize);
  this.onResize();
  @@ -353,6 +354,7 @@ module.exports = React.createClass({
  MatrixClientPeg.get().removeListener("accountData", this.onAccountData);
  }
  + window.removeEventListener('beforeunload', this.onPageUnload);
  window.removeEventListener('resize', this.onResize);
  document.removeEventListener("keydown", this.onKeyDown);
  @@ -365,6 +367,14 @@ module.exports = React.createClass({
  // Tinter.tint(); // reset colourscheme
  },
  + onPageUnload(event) {
  + if (ContentMessages.getCurrentUploads().length > 0) {
  + return event.returnValue =
  + 'You seem to be uploading files, are you sure you want to quit?';
  + }
  + },
  +
  +
  onKeyDown: function(ev) {
  let handled = false;
  const isMac = navigator.platform.toUpperCase().indexOf('MAC') >= 0;
  