Added methods to canvas_data to support drawing an offscreen canvas onto another canvas
Bug fix: Swapped OffscreenCanvas width and height parameters to match Mozilla spec
Tests: Updated metadata for 866 tests
There are a few canvas2d-related dependencies that haven't updated, but they
only use euclid internally so that's not blocking landing the rest of the
changes.
Given the size of this patch, I think it's useful to get this landed as-is.