The first such case, as noticed by Google Operating System, is RealPlayer, which offers you to install Chrome during its own installation process. As far as Google's software goes, you also get the option of installing Chrome when you install Google Earth.
It's a fairly standard affair; you'll see Yahoo toolbar and many other applications bundled with other apps in a similar manner. It is, however, slightly unusual for Google, which is used to gaining huge market shares in very short periods of time with nearly everything they do. It's not a surprise that Chrome's market share is going up slowly; the browser market is quite saturated, and notoriously hard to penetrate due to the fact that many users tend to use whatever comes with the OS and stick with it no matter what.