初识Watcher章节,Watcher构造函数中this.dirty应该是true

[JYDwayne]

源码中是:
this.cb = cb
this.id = ++uid // uid for batching
this.active = true
this.dirty = this.lazy // for lazy watchers

文中的表述是:
this.cb = cb
this.id = ++uid // uid for batching
this.active = true
this.dirty = this.computed // for computed watchers