DumpRenderTree needs dumpAsText as well in order for dumpChildFramesAsText to work, whereas WTR doesn't. Tentatively fix this inconsistency in DRT.
Pull request: https://github.com/WebKit/WebKit/pull/6969
<rdar://problem/102815775>
Committed 257221@main (6155452b4f34): <https://commits.webkit.org/257221@main> Reviewed commits have been landed. Closing PR #6969 and removing active labels.