message: fix TSpan default style
diff: @@ -2,7 +2,7 @@ import Displayable, { DisplayableProps, DisplayableStatePropNames } from './Disp
  import { getBoundingRect, DEFAULT_FONT } from '../contain/text';
  import BoundingRect from '../core/BoundingRect';
  import { PathStyleProps, DEFAULT_PATH_STYLE } from './Path';
  -import { extend, createObject } from '../core/util';
  +import { createObject, defaults } from '../core/util';
  export interface TSpanStyleProps extends PathStyleProps {
  @@ -19,7 +19,7 @@ export interface TSpanStyleProps extends PathStyleProps {
  textBaseline?: CanvasTextBaseline
  }
  -export const DEFAULT_TSPAN_STYLE: TSpanStyleProps = extend({
  +export const DEFAULT_TSPAN_STYLE: TSpanStyleProps = defaults({
  strokeFirst: true,
  font: DEFAULT_FONT,
  x: 0,
  