Patrick Altoft at BlogStorm spotted the test, providing the screenshot below and saying, "One of the fascinating things about this is that they are highlighting certain sections of the page in orange and expanding the text to provide a snippet of information. This shows that they have the technology to know exactly where a piece of text is on every single web page. The snippets highlighted are not always the same as the snippet in the search results."
Image credit: Patrick Altoft at BlogStorm
While this may not be a widely released feature yet (and it's possible that it won't be), it's interesting to see just how much Google has changed the search experience this year, just from the desktop. In the Spring, Google rolled out the left panel navigation. More recently, they introduced Google Instant. Those are the major changes, though there have been other smaller ones sprinkled in among them.