From http://en.wikipedia.org/wiki/Chromium_(web_browser):

 Chromium is the name given to the open source project and the browser source code released and maintained by the Chromium Project. It is possible to download the source code and build it manually on many platforms. Google takes this source code and adds (to Chrome):

• an integrated Flash Player
• a built-in sandboxed PDF viewer
• the Google name and logo
• an auto-updater system called GoogleUpdate
• an opt-in option for users to send Google their usage statistics and crash reports
• RLZ tracking when Chrome is downloaded as part of marketing promotions and distribution partnerships. This transmits information in encoded form to Google, e.g. when and from where Chrome has been downloaded. In June 2010, Google confirmed that the RLZ tracking token is not present in versions of Chrome downloaded from the Google website directly or in any version of Chromium. The RLZ source code was also made open source at the same time so that developers can confirm what it is and how it works.