Keyboard shortcut for Spotlight doesn't work in full screen Google Chrome on Mac OS X 10.7 (Lion)
Chrome doesn't currently support Lion's full screen features. They are working on a version that does.

Until that is finished, you'll have to use Chrome's built-in full screen capabilities (not based on Lion's).

You can change the keyboard shortcut to enter that the same way you'd change any other (System Preferences-> Keyboard-> Keyboard Shortctus-> [+] button