Looks like this git pull is related: https://github.com/w3c/web-platform-tests/issues/4802.

Reza: should I wait for you to finish testharness-ify the toBlob/toDataURL tests first?

Those that need to change are already uploaded:

https://codereview.chromium.org/2695963004
https://codereview.chromium.org/2693043012

They need Justin's lgtm to land.

FYI: The issue https://github.com/w3c/web-platform-tests/issues/4802
is strictly about the encode failure.  We can test it in Chrome by trying to encode a large canvas into a image/webp, but that will not work in other browsers, so we can<t test that in WPT.

We already have 3 tests about canvas.toBlob() in html/semantics/embedded-content/the-canvas-element/. Maybe that's sufficient? Or maybe we want to move more from LayoutTests to wpt. Assigning this to zakerinasab@ to decide whether this issue can be closed now.