Hi Valeria,
Thanks for the test case.
I can see the frame rate degradation. The cause is most visible using the Chrome-specific tool about:tracing (just put that in the URL bar), recording, and then "JavaScript & Rendering" trace. Here's a screenshot.
Basically - it looks like your application eventually falls a few frames behind (maybe because it's GPU bound?), at which point Chrome starts waiting for the 3rd oldest frame to finish rendering before it'll start processing the rendering commands for the next one. At this point, it becomes very slow.
Looking at the output of the --show-mac-overlay-borders command line argument (
documentation), nothing out of the ordinary seems to be going on.
I have to apologize, but we don't have enough people on our team to diagnose every application in detail. I suggest that you try cutting down your application's rendering and figure out what about it causes this performance drop - if you can eliminate the performance drop over time, that's good information. Or, start from the other direction - a minimal test case just clearing the large canvas to a solid color in pure JavaScript. If you can provoke the slowdown in that configuration, please file a bug at
https://crbug.com/ , attach the test case, and post the bug ID here so we can be sure to triage it.
-Ken