Editor does not focus to the sentence when redo or undo

This issue is happening not only in my local machine but also happening in trix editor demo site ( https://trix-editor.org/ ) as well.

##### Steps to Reproduce
Write some paragraphs so that page scroll can go down.
Then make few words as bold which are somewhere on the top section of the content and then scroll down again to the end of the content.
Then try to Undo / Redo .

##### Actual Behavior:
the content was getting changed (unbold / bold) while doing Undo / Redo . But the page scroll focus did not reach to that section. It was still on the end of content.

##### Expectation:
page scroll will focus to that section where Undo / Redo is happening.

No files or tests are named. Start by reproducing the steps in the Trix editor demo at https://trix-editor.org/, then trace the undo/redo behavior and how the editor handles the current selection and scroll position. Done means undo and redo move the page focus to the changed sentence while preserving the existing content change.

Written by the indexing model from the issue text.