Missing undef MESSAGE_CHECK in WebFrameProxy.cpp causes building errors when we add new files and try to compile unified build.
Pull request: https://github.com/WebKit/WebKit/pull/6033
Committed 256233@main (628f0ba433d8): <https://commits.webkit.org/256233@main> Reviewed commits have been landed. Closing PR #6033 and removing active labels.
<rdar://problem/101863655>