message: Fix issue with sticker picker rendering off-screen
  when the RightPanel is collapsed on a small monitor
  and the sticker picker is opened.
diff: @@ -252,16 +252,33 @@ export default class Stickerpicker extends React.Component {
  * @param {Event} e Event that triggered the function
  */
  _onShowStickersClick(e) {
  + // XXX: Simplify by using a context menu that is positioned relative to the sticker picker button
  +
  const buttonRect = e.target.getBoundingClientRect();
  // The window X and Y offsets are to adjust position when zoomed in to page
  - const x = buttonRect.right + window.pageXOffset - 42;
  + let x = buttonRect.right + window.pageXOffset - 41;
  +
  + // Amount of horizontal space between the right of menu and the right of the viewport
  + // (10 = amount needed to make chevron centrally aligned)
  + const rightPad = 10;
  +
  + // When the sticker picker would be displayed off of the viewport, adjust x
  + // (302 = width of context menu, including borders)
  + x = Math.min(x, document.body.clientWidth - (302 + rightPad));
  +
  + // Offset the chevron location, which is relative to the left of the context menu
  + // (10 = offset when context menu would not be displayed off viewport)
  + // (8 = value required in practice (possibly 10 - 2 where the 2 = context menu borders)
  + const stickerPickerChevronOffset = Math.max(10, 8 + window.pageXOffset + buttonRect.left - x);
  +
  const y = (buttonRect.top + (buttonRect.height / 2) + window.pageYOffset) - 19;
  this.setState({
  showStickers: true,
  stickerPickerX: x,
  stickerPickerY: y,
  + stickerPickerChevronOffset,
  });
  }
  @@ -314,7 +331,7 @@ export default class Stickerpicker extends React.Component {
  const stickerPicker = <ContextualMenu
  elementClass={GenericElementContextMenu}
  - chevronOffset={10}
  + chevronOffset={this.state.stickerPickerChevronOffset}
  chevronFace={'bottom'}
  left={this.state.stickerPickerX}
  top={this.state.stickerPickerY}
  