Resync Source/ThirdParty/libwebrtc/Source/webrtc/test/testsupport/file_utils_unittest.cc as it has merge conflicts
<rdar://problem/102804676>
Pull request: https://github.com/WebKit/WebKit/pull/6963
Committed 257244@main (e0a92e883570): <https://commits.webkit.org/257244@main> Reviewed commits have been landed. Closing PR #6963 and removing active labels.