See https://chromium-review.googlesource.com/c/chromium/src/+/834885/4/third_party/WebKit/LayoutTests/fast/events/inputevents/inputevent-ime.html#196

We fire the textInput event to signal that an IME is actually finished composing text. Right now we fire it for CommitText(), but not FinishComposingText() with an open composition, which seems inconsistent. 

Note: textInput is deprecated and we may remove it, in which case this issue will be moot:
https://bugs.chromium.org/p/chromium/issues/detail?id=701480