Google has just released an update for the Chrome browser's stable branch that fixes several security vulnerabilities and adds several new features to the browser. The two most prominent feature additions in Chrome 17 are Omnibox Prerendering and Download Scanning.
The second new feature is the automatic scanning of executable files like exe or msi in Chrome to warn you if you are downloading a malicious file or a file from a host that is know to host a high percentage of malicious downloads.
Google maintains a whitelist of files that are not checked. All other files are checked with Google to retrieve more information. While not a fail safe approach, it can warn users if they are about to download known malicious files. The concept looks similar to Microsoft's SmartScreen Filter. It does not seem possible to disable the feature right now in the browser.
In addition, a total of 20 security vulnerabilities were closed in Chrome 17 of which one received the highest possible severity rating of critical.
You can read up on the changes at the official Chrome Release blog . Chrome updates should already been applied to existing Chrome Stable installations. You can verify the version with a click on Wrench > About Google Chrome. There you can also download and apply the update if the browser has not been updated yet.