Google Chrome	53.0.2785.70 (Official Build) beta (64-bit)
Platform	8530.62.0 (Official Build) beta-channel samus

What steps will reproduce the problem?

(1) Open chrome://settings
(2) Show Languages and input setting 
(3) Add Japanese
(4) Check "Google Japanese input (for US keyboard)"
(5) Close chrome://settings
(6) Open a new tab
(7) Focus Omnibox
(8) Press Ctrl+space several times to switch to the Japanese IME (you'll see "あ" instead of "US" in the tray.)
(9) Press a, confirm あ (with underline) is shown.
(10) Press Ctrl+space to switch back to "US" mode.

What is the expected output?

* あ without underline is in Omnibox. 
* The IME is not active. "US" in the tray.

What do you see instead?

* "あ " (two characters, あ with a space) *with* underline is in Omnibox.
* The IME is still active. "あ" in the tray.

Please use labels and text to provide additional information.

I guess this is a recent regression. Please triage. Since the other IME toggle shortcut (Shift+Alt) was removed, I'm now forced to use Ctrl+space for toggling IME, and Ctrl+space does not work as intended, which is sad...