Chrome Beta for Android has a flag called "Enable contextual search". You can find it by opening a new tab, pasting this in the address bar: chrome://flags/#contextual-search and pressing Enter. If you click "Enable" and "Relaunch now" at the bottom of the page, you'll enable this new feature.
What happens after enabling the feature? Tap a word from a page and Google will display it at the bottom of the page next to other surrounding words and a Google logo. Tap the logo and Chrome sends you to an internal Google page you can't access. The URL starts with: https://layers.sandbox.google.com/contextualsearch and includes the word you've tapped, the context and the URL of the page.
It's not clear what's the goal of this feature, but I assume that Google might show some search results related to the words you've selected and the context.
{ Thanks, Jérôme Flipo. }