This is a heads up that we are considering changing the spec of getImageData() to improve interoperability.
The gist of it is we are changing the IDL signature of the function from double to long, removing edge cases (dimensions in (0,1) range) and adding web platform tests.
This is the relevant issue: https://github.com/whatwg/html/issues/2433
I'll update this with the spec and web-platform change when appropriate.
Just FYI, the spec and web-platform changes are in: