[macOS] Constant frame dropping during Flash video playback

[macOS] Constant frame dropping during Flash video playback
https://bugs.webkit.org/show_bug.cgi?id=181249
<rdar://problem/34843448>

Reviewed by Eric Carlson.

Review of logs during jerky flash video playback shows a few IOKit properties are being blocked by the sandbox,
which prevents some high-efficiency codecs from being used. Add 'AppleGVAKeyDoesNotExist', 'IODVDBundleName', and
'IOGVA*Encode' to the whitelist.

* PluginProcess/mac/com.apple.WebKit.plugin-common.sb.in:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@226369 268f45cc-cd09-0410-ab3c-d52691b4dbfc