Google has developed a search box that will appear on the left-hand navigation to save people having to tab out and opening another search box while using Gmail.
I have had similar situations as the one described in the Gmail blog:
"I used to have a problem. People would ask me questions, over chat or email, and I'd have to leave Gmail to search Google for an answer. Then I'd have to select the answer, copy it, go back to Gmail and paste the answer into the chat window or my reply. Sometimes I'd get distracted and forget to go back to Gmail, and I'd have to go through it all again when I remembered what I'd been doing."
You can add it through the Gmail Labs settings and is very handy, as the picture shows below.
As the image shows you can then choose to drop the result you want into chat or an email.
Thanks Google this one will be very handy.