Google has recently released a plugin for Internet Explorer that renders web pages using Google Chrome. The plugin, called Google Chrome Frame, is open-source and the code is publicly available.
By looking at the code, it's obvious that the plugin is not limited to Internet Explorer. There's also a NPAPI plugin, which should work in browsers that support NPAPI: Firefox, Safari, Opera and other browsers. Here's a comment from one of the Chrome Frame files:
"ChromeFrameNPAPI: Implementation of the NPAPI plugin, which is responsible for hosting a chrome frame, i.e. an iframe like widget which hosts the the chrome window. This object delegates to Chrome.exe (via the Chrome IPC-based automation mechanism) for the actual rendering".
Instead of asking users to download a different browser, Google and other companies that develop complex web applications can ask users to install Google Chrome Frame. This way, Google Chrome runs invisibly inside another browser.
Jim Jarmo's Puntastic
34 minutes ago