I do not know the history of window docking and snapping, but I saw this thing first on Windows 8. Now with the latest update to Chrome OS, I can do this on my Chromebook too.
Window snapping/docking can be enabled on Chromebook using a keyboard shortcut. We can now use the <Alt> + ] and <Alt> + [ keys to side dock, snap and restore windows..
To give this a try, open couple of windows on your Chromebook and try those keyboard shortcut to rearrange how they are positioned on the desktop. This is going to be useful when you have to look at two separate websites or apps at the same time to do some work. I tried this with the Google Keep app to take notes and it worked really well!
If you are on the Dev channel, go ahead and try this now. For Beta and Stable channel users, wait for a few more weeks and this will be on your Chromebooks too!
via François Beaufort