Once you have enabled the chat in your Settings page in Gmail, you can now see YouTube videos within the chat window. Google shows a
preview of the YouTube video in chat.
Without this new feature, you have to open the link in a new window, which disturbs your current chat conversations with friends.
An example of the chat conversation is shown below:
See YouTube videos in Gmail Chat
Gmailblog.blogspot.com
The YouTube video appears in a small screen, so when you click the “play” icon, you can watch the video while you chat.
This YouTube preview is available only within Gmail platform, it is not available in
Google Talk chat platform. It is not clear why it is not available in the main Google Talk platform.