Chrome's inspector tools allow for "throttling" the loading of your site, so you can test what a user on a 3G connection might experience.

To utilize/test loading your site with the different network speeds:

1. Open the inspector (right click anywhere on the webpage and choose "inspect").
   
    
2. In the resulting panel or window, click "Network" to open the network tab.
   
    
3. Look for the "throttling" selector.
   
    
4. Click on it to reveal the options; select your desired network speed/connection.
   
    
5. Perform a hard refresh/reload of the page (command-shift-r)

After the page loads, you can inspect the "time" column of the network panel to see what took the longest to load.