Please note that Hijack page scrolling like Google Plus? asks for a very different stuff.
In the following screenshot from Google+ the red box shows the area which scrolls. All other portions, for example, the left navigation is static. I am very intrigued by their UI. You can scroll the center part even when your mouse is over the navigation section or any other fixed part.
Any idea how do they do it?

The UI components are probably all in
display: fixedCSS blocks, which pin them to the browser window, regardless of scrolling. Then the main content can be in a regular block, which scrolls with the page.