The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/308f9ad3c2a3c91523c5efbbd426a533646d9d5c

commit 308f9ad3c2a3c91523c5efbbd426a533646d9d5c
Author: Ryan Landay <rlanday@chromium.org>
Date: Fri Jan 12 21:08:58 2018

Don't fire beforeinput and textInput events for no-op CommitText()

Currently, if an IME calls InputMethodController::CommitText() with no
composition open and passes an empty string, we fire the beforeinput and
textInput events (but *not* the input event). For consistency, it seems that we
should not fire any events in this case, since the edit operation doesn't
actually do anything.

Note: it *is* theoretically possible for an IME to use CommitText() with an
empty string just to move the selection. I'm not sure if this ever happens in
practice or not.

Bug:  796691 
Change-Id: Ic13acc6842e92910e9c5ce7842f8f7b908fdec42
Reviewed-on: https://chromium-review.googlesource.com/862517
Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Ryan Landay <rlanday@chromium.org>
Cr-Commit-Position: refs/heads/master@{#529067}
[modify] https://crrev.com/308f9ad3c2a3c91523c5efbbd426a533646d9d5c/third_party/WebKit/LayoutTests/fast/events/inputevents/inputevent-ime.html
[modify] https://crrev.com/308f9ad3c2a3c91523c5efbbd426a533646d9d5c/third_party/WebKit/Source/core/editing/ime/InputMethodController.cpp
[modify] https://crrev.com/308f9ad3c2a3c91523c5efbbd426a533646d9d5c/third_party/WebKit/Source/core/editing/ime/InputMethodControllerTest.cpp