The most recent addition to Gmail Labs is a feature that lets you quickly add Google search results to a message. Instead of opening a new tab, typing the query and copying the results, you can now search directly from Gmail. The box that shows up lets you copy the results or just the web addresses, but you can also drag the links to your message.
Currently this features only allow you to search in normal Google web serach, but not including the images, videos, local businesses, maps, products and etc. I believe that sooner or later, Gmail Labs team will annouce the update version for the Google search features in Gmail.
How to enabled Google Search in Gmail:
Basically the way to enabled Google Sarch features in Gmail are the same as other, just go to the Google Labs at the top right corner of your Gmail home page, then search for the word of Google Search, then just enable it and save the change. Then you found that the Google Search tools box will appear on your Gmail left panel.