image with src set to data:image/png should be considered as same origin, as we fixed in Bug 1373513. So this reverts what we did in bug 1363673.
Once we turn off security.data_uri.inherit_security_context, data: URI will be considered as a CORS request, so those tests replying on canvas.toDataURL() will fail if crossorigin is not specified. So I add crossorigin attribute into those <image>.
Followed by P1, we can use resources in dom/canvas/test now. MozReview-Commit-ID: 4Pnj1fbcze4
MozReview-Commit-ID: 9AXLGuZ5I2t
