Enable Image Observer by default in WebKit1
I wonder how much of the problem described in https://twitter.com/html5test/status/1456304856696827918 is this bug.
Potentially also https://github.com/Financial-Times/polyfill-library/issues/1192
Pull request: https://github.com/WebKit/WebKit/pull/1681
Committed 251787@main (ea72d728429e): <https://commits.webkit.org/251787@main>
Reviewed commits have been landed. Closing PR #1681 and removing active labels.