version 65.0.3322.0 (offical build) dev (64 bit)
Platform 10315.0.0（official build) dev-channel link 
Firmware Google_Link.2695.1.169


REPRO STEPS:
1.Disable Voice input (flag:#disable-voice-input)
2.Switch to Pinyin input method
3.Tap any keys to make Candidates&Down Arrow appear
4.Click on any candidate to submit it
5.Switch to any other language (e.g. US)
6.Switch to Floating keyboard

Actual result: 
4.1 Suggestion empty, but Down Arrow still not disappear.
5.1 Down Arrow still not disappear.
6.1 Down Arrow still not disappear.
 

Deleted: Jan 18 2018 1_37 PM.webm 1.7 MB

	Jan 18 2018 1_37 PM.webm 1.7 MB View Download