We can now develop Chrome OS applications that include parts developed in C\C++. You can find more information about the Chrome OS Native Client SDK at http://code.google.com/chrome/nativeclient/.
The code written in C\C++ can render 3D graphics, interact with the mouse, play rich media, run on multiple threads and even access the memory directly.
The end users are not required to install a plugin. Chrome OS applications that include portions developed in C\C++ can run out of the box without any special preparation.
The code written in C\C++ runs on all platform. There is no need to port it for the various platforms. Similarly to Java applets.