Google announced on Google+ that the Chrome app for Android will now detect your bandwidth speed on your device and if it is slow, it will first load the web site without the images and then load in the images after the fact. Google said this can save 70% of your data.
Here is how Google put it:
If we detect low bandwidth, the Chrome Android app loads websites without the images first, saving you 70% data.
This is rolling out to Chrome app Android users in India and Indonesia first. It may then roll out to more users later.
How does this differ from Google Web Light? Well, this will load the original web site just do it in a specific order, whereas Web Light loads a scaled back version of your site on a Google URL.
Here is an animated GIF from Google on how it may look:
I am not a 100% sure how this impacts ads.
Forum discussion at Google+.