message: play button toggles playback
diff: import React from "react";
  import { observer } from "mobx-react";
  import PlayAll from "../../components/ActionButtons/PlayAll";
  -import PlayCurrent from "../../components/ActionButtons/PlayCurrent";
  import Pause from "../../components/ActionButtons/Pause";
  import StepInto from "../../components/ActionButtons/StepInto";
  import SpeedGauge from "../../components/ActionButtons/SpeedGauge";
  import Record from "../../components/ActionButtons/Record";
  import UiState from "../../stores/view/UiState";
  +import PlaybackState from "../../stores/view/PlaybackState";
  @observer
  export default class ToolBar extends React.Component {
  render() {
  return (
  <span>
  - <PlayAll />
  - <PlayCurrent />
  + <PlayAll onClick={PlaybackState.togglePlaying} />
  <Pause />
  <StepInto />
  <SpeedGauge />
  