Version: 55.0.2865.0 (Official Build) canary (64-bit)
OS: macOS 10.11.6

What steps will reproduce the problem?
(1) In Gmail, reply to the last email in a thread.
(2) Scroll down.
(3) Scroll up, expand the first message in the thread, and scroll down again.

What is the expected output?

Expect the compose box to render correctly.


What do you see instead?

The bar containing the "Send" button, discard (trash) icon, etc. is drawn over the message content at various places. It's clear it's just a rendering bug because clicking on the message to edit it at those points causes the text to redraw correctly.

This is a regression within the past couple of Canaries. I noticed strange redraw behavior of the Send bar on Friday (half of it was redrawn when pressing return to grow the compose box), but this seems new.

Guessing that this is a paint invalidation bug, and CC'ing a couple of people who might be working in this area.

Here's a screenshot. Accessible to Google employees only, sorry.
https://drive.google.com/a/google.com/file/d/0B5DES7PYkZBLdmhPNV9Md0prLVE/view?usp=sharing