GトークでYouTube

これ、結構使えそうです。
Gトーク（Gメールのチャット機能）上でYouTubeの動画が見れるんです！
Watch videos right in Gmail chat

My friends always hate it when I multi-task in other tabs while chatting with them (they can tell because of my obviously delayed reactions...). But sometimes it's not my fault: if they send me a link to a YouTube video, I have to open another tab in order to watch it. To help with this, we've just added a new feature to Gmail chat: YouTube and Google Video previews. If you receive (or send) a link to a video in a chat message, you'll see a preview of the video right in your chat window.

Click the preview, and the video will play right there. Just remember to say something every once in a while or your friends will probably catch on that you're enjoying the dramatic chipmunk more than their conversation...

実際に試してみました。

プリビューって書いてあるから最初の30秒くらいしか見れないのかと思ったら、ふつーに1分の動画見れて、３分のを試したら全部見れて、10分のも全部見れました！

個人的にYouTubeの動画は自分で探すのではなくって誰かに送ってもらったのを見るのが圧倒的に多いので、非常に使えるかなと。