At the beginning of this month Gmail started supporting attachments of up to 50MB at long last, and today's feature addition to the web-based client probably has something to do with that. Rolling out in the next 15 days to all Gmail users is a video streaming capability for attachments. This means you will no longer be required to download a video attachment in order to watch it. Once this reaches you, video attachments will show a thumbnail from the clip. When you double-click on that, the content will just start streaming inside a video player that's very similar to the one YouTube...
Source: http://www.gsmarena.com/gmail_can_now_stream_video_attachments-news-24011.php
