"If you sign in to Chrome browser, Chrome OS or an Android device that includes Chrome as a preinstalled application with your Google Account, this will enable the synchronization feature. Google will store certain information, such as HISTORY, bookmarked URLs as well as an image and a sample of text from the bookmarked page, passwords and other settings, on Google's servers "
And this isn't that far from full browsing behavior.And that's from a few minutes reading this page - we don't know if they track deeper details - like how long the page was open.
Also - Google doesn't have to collect this data. The claimed purpose of this is that you could share history on multiple devices. But this can also be achieved by sending encrypted history to Google and decrypting the history on each device you use(i think browser extensions with similar functions implement this in that way). So it's clear the purpose here is collecting data.