Able to reproduce on Windows-10, Ubuntu 14.04 and Mac OS 10.12 using chrome stable M57-57.0.2987.98.

Bisect Information:
=====================
Good build: 57.0.2978.0
Bad Build : 57.0.2980.0

You are probably looking for a change made after 442829 (known good), but no later than 442830 (first known bad).

Change Log URL: 
https://chromium.googlesource.com/chromium/src/+log/0c11ed986f2c7da313eaca87d592b6bd21cee383..c5291a0115a65797dbf7992c8aa47136db95ae6a

From the above change log suspecting below change
Review URL: https://codereview.chromium.org/2517383002

joone.hur@ - Could you please check whether this is caused with respect to your change, if not please help us in assigning it to the right owner.

Note: Since this issue got regressed in chrome M-57 adding RB-Stable, Please feel free to edit if this is not the case.

Thanks!

The change to have the caret match the font size rather than line height is perfectly fine and mostly matches the behavior in Edge and Mozilla (they both appear to size it according to the the majority of the text rather than change it mid sentence though).

When stepping through left to right the caret changes size as appropriate upon encountering the dinosaur. When going right to left however it is positioned correctly but sized incorrectly for the position imminently following the dinosaur.

This isn't great but it doesn't break any of the editing or selection behavior. I'd we should prioritize fixing this but that it isn't bad enough to block 57 on.

Thank you very much  eae@. Moving forward with today's Stable release.