This release of the Viewer pulls in a raft of updates to the built in media support that were not quite ready to be integrated when the 64 bit Viewer (Alex Ivy) was released.
It is comprised of various fixes, updates, security patches and improvements for CEF (Chromium Embedded Framework) that is the basis for the built in web browser and VLC that provides support for video media playback.
In addition fixes are included to Dullahan (the third party library that uses CEF) as well as all the media plugin code itself.
As per the Alex Ivy 64 bit viewer, there is no Linux version.
The option to not accept cookies has been removed due to complexities of not doing so in the in-viewer browser. For a more controlled cookie experience, an external full-featured browser may be better.