framebufferOrigin property
Top left, like Metal and Impeller and unlike OpenGL. WebGPU's framebuffer coordinates start at the top left corner and its attachments are written from there, so nothing has to be turned over anywhere: an uploaded image and a rendered one are the same way up, which is the pair the WebGL2 backend has to keep apart with a flag on every texture.
Implementation
@override
FramebufferOrigin get framebufferOrigin => FramebufferOrigin.topLeft;