Remove VP8/9 and WebM-related system feature flags
Created attachment 456613 [details] Patch
Created attachment 456621 [details] Patch
Created attachment 456636 [details] Patch
Created attachment 456644 [details] Patch
Committed r292358 (249223@trunk): <https://commits.webkit.org/249223@trunk>
<rdar://problem/91270253>