According to http://www.whatwg.org/specs/web-apps/current-work/#dom-context-2d-createimagedata, createImageData should create an ImageData object with width and height equal to the absolute magnitude of the values passed to createImageData. WebKit currently does not do this.
Created attachment 35122 [details] Handle negatives properly Proposed fix for this bug.
Created attachment 35125 [details] Include layout tests Woops, old patch didn't include the layout tests for some reason.
Comment on attachment 35125 [details] Include layout tests Seems that this test should be a dumpAsText cross-platform test, the way many of the tests in fast/canvas are, such as canvas-alphaImageData-behavior.html for example. That would be more valuable than one with platform-specific results. r=me as is, but please consider making that change
Comment on attachment 35125 [details] Include layout tests Since George isn't a committer and won't be able to commit this when landing, marking this r- per Darin's above comments. I agree, this would be nicer as a dumpAsText test.
I fixed this with http://trac.webkit.org/changeset/59613 (bug 39189)