I found that Scroll.batchEnd could not always record the recorret mutations when fire compositionend event.

Steps for Reproduction
0. all steps below should type except english to make compositionend function fired.

1. type "###" + something in editor, then press "enter"
2. ctrl + A, and press "del"
3. type repeat step one, and then press "enter"

Expected behavior:
new line should be append after what we typed

Actual behavior:
new line append before what we typed.
And I found that when second type "#", when batchend function fired, batch object is empty Array, but when first typed, there was an Array with three mutation record

• remove br element
• append text element
• change characterData

Platforms:
Chrome browser, version 88.0.4324.182

Version:
2.0.0-dev.4

I has made some fix to make my program run correctly, but I don't think this is a good way. I think I should check the delete function to find out why mutation was not observed before batchend function fired

Scroll.prototype.batchEnd = function () {
  const mutations = this.batch;
  this.batch = false;
  this.update(mutations.length ? mutations : undefined);
}