Add notes pointing to the relevant requirement for fetching a data URL with a non-GET method.
Merge pull request #1230 from Ms2ger/comment-xhr-data-url

Add notes pointing to the relevant requirement for fetching a data URL with a non-GET method; r=annevk
Remove reference to a now-fixed bug.
Merge pull request #1231 from Ms2ger/26353-comment

Remove reference to a now-fixed bug.