How we deal with Canvas Support

We have 2 implementations of Container Timing, in both Firefox and Chromium.
Chromium doesn't support canvas right now, so the canvas example yields no PerformanceContainerTiming entries, however the Firefox example does.

The way the Firefox one works is it will yield a single Container Timing entry on the first paint of a canvas element and the size of that entry is the entire canvas, this means we'll only ever get one entry per canvas element as the paint checking isn't more granular than that. I suppose this is working as expected, similar to an image which will take up the full area regardless of what the image is made up off.

Are there any thoughts on this approach?

Start with examples/canvas-2d and compare the Firefox and Chromium implementations described in the issue. Read the linked Firefox change to understand the single-entry behavior and canvas sizing, then review the discussion before proposing a documented decision about the approach.