Unable to type Japanese characters correctly in a table with Chrome 65+ in case that the more left cell is not empty

Summary

We cannot type Japanese characters correctly in a table with Chrome 65+ in case that the more left cell is not empty.

Japanese character is generally composed of consonant+vowel letter combination like "k" + "i" = "き" and Japanese IME helps the conversion.
However, such conversion doesn't work as expected in the specific condition.

Also, this problem is not reproducible with Chrome v63 and the prior versions. This problem might be related to some spec change in Chrome.

Environment

Client that runs the browser is

• Windows and macOS
• Chrome (Tested with ver. 65.0.3325.162)
• Microsoft IME (Japanese) , Google Japanese IME, and Mac IME (Japanese) (This means this occurs in any IME.)

Steps to Reproduce

1. Create a blank page.
2. Create a table with more than two columns.
3. Type some character (e.g. "a") in a cell in the first column.
   
4. Set IME to Japanese.
5. Try to type some Japanese character (e.g. "き") in a cell more right from the cell in Step 3.
   You need to type "k" + "i" in order to compose the Japanese character "き".

Expected Results

"k" + "i" should be always converted to "き" with Japanese IME. ("ki" = "き" in Japanese)
Firefox.mov

Actual Results

"k" + "i" becomes "kい". The initial consonant letter is auto-committed. ("i" = "い" in Japanese)

GoogleIME.mov
MicrosoftIME.mov

Notes

• Please note this symptom is different from the issue CONFSERVER-54326 because it reports that first letter is "ignored" while the letter is "auto-committed" in this case.
• This occurs only at the Chrome environment, and IE11 also has another issue(Cannot type double byte characters in Section through IE11). Firefox works fine.
• As mentioning in the above, this problem might be related to some spec change in Chrome.
  • This has not occurred on Chrome v63.x and prior.
  • The very similar behavior can be seen in different products (e.g. Slack) aside from Atlassian's ones
    • Latest Chrome 65 update breaks start of CJK IME input · Issue #2009 · quilljs/quill · GitHub
    • 576573 - Japanese IME: First character is auto-committed on office extensions - chromium - Monorail (This is a bit old report, however still opened.)
    • Google Groups – Chrome 65 アップデート後 Slack で一文字目が意図せず確定される問題について

Workaround

• Delete the affected letter, and re-type the contents.
• Use Firefox browser.