> For instance, in Chrome for Android 80% of the touch events that block scrolling never actually prevent it

I'm curious how they get at this data. I haven't fully thought it through, but something about this raises the "creepy flag" in my head.

Does this data come through the "Automatically send usage statistics and crash reports to Google" setting? Google's help page [1] regarding that doesn't seem to indicate it's recording information about website's javascript.

[1]: https://support.google.com/a/answer/151135?hl=en

EDIT: I'd also be curious if they have done any analysis to see if the mechanism that gathers this data is related to the performance implications of touchEvent listeners.