Chrome Dev Tools already supports many types of emulations to simplify the development and testing on other platforms and environments, like emulating touch events, devices, screen resolutions etc. Interested users should follow this guide to learn more about these features.
Latest addition in Dev Tools emulation feature is the network emulation which allows developers to control network speed. Users can emulate typical EDGE, GPRS and 3G speeds. They can even set the network to offline in order to test the offline features of web sites and apps (though not working for me, at the moment).
The network emulation feature is currently available in the Canary and Dev channels of Chrome and ChromeOS, and should arrive to the stable channel in coming weeks.