Make soft linked AVCaptureDeviceType strings optional
<rdar://problem/107581953>
Pull request: https://github.com/WebKit/WebKit/pull/12343
<rdar://106004017>
Committed 262593@main (8c2d475507f7): <https://commits.webkit.org/262593@main> Reviewed commits have been landed. Closing PR #12343 and removing active labels.
Re-opening for pull request https://github.com/apple/WebKit/pull/540
Pull request: https://github.com/apple/WebKit/pull/541
Committed 259548.631@safari-7615-branch (48875b2d1190): <https://commits.webkit.org/259548.631@safari-7615-branch> Reviewed commits have been landed. Closing PR #541 and removing active labels.