Repro steps:

1. Create a flutter app with two textfields
2. Focus the cursor in the first textfield
3. Switch to Japanese input mode and enter text (e.g. type, one character at a time: n i h o n n g o)
4. Without committing (Return) or cancelling (Escape) input, focus the curse in the second text field

Expected behaviour: the OS/framework arenotified that the composing (mark) text is committed, and that the OS mark text should be cleared

Actual behaviour: IME state still contains the same composing (mark) text as it had when composing in the first text field. The first textfield behaves as though the compose (mark) text was committed but that's likely because we send compose text inline with the full text string, and compose start/end position separately. The framework still likely thinks the field is composing.