code: function() {
      this.appendDummyInput()
          .appendField(new Blockly.FieldIconMenu(
              [
                {src: Blockly.mainWorkspace.options.pathToMedia + 'icons/wedo_motor-speed_slow.svg',
                  value: 'slow', width: 48, height: 48, alt: 'Slow'},
                {src: Blockly.mainWorkspace.options.pathToMedia + 'icons/wedo_motor-speed_med.svg',
                  value: 'medium', width: 48, height: 48, alt: 'Medium'},
                {src: Blockly.mainWorkspace.options.pathToMedia + 'icons/wedo_motor-speed_fast.svg',
                  value: 'fast', width: 48, height: 48, alt: 'Fast'}
              ]), 'CHOICE');
      this.setOutput(true);
      this.setColour(Blockly.Colours.motion.primary,
          Blockly.Colours.motion.secondary,
          Blockly.Colours.motion.tertiary
      );
    }
docs: Block for motor speed drop-down (used for shadow).
  @this Blockly.Block