According to common.css, its 759px where the columns recieve some adjustment. Then at lesser resolutions, other elements change.
Have a look through here:
http://mydevice.io/devices/and here
http://www.websitedimensions.com/Be aware though, responsive webdesign has changed a whole heck of a lot in just 2016 alone. Also, the end of 2015 is when people started noticing Phablets as being a thing. Even though the Galaxy Tab had already been around for a few years, the resolution on them sucked. The Nexus6 was Google's first Phablet. Your PixelC was released almost one year after Shamu and Flounder... man, I really do hate the Flounder (had a 32GB version. Died after 4 months. Bad nand....all 2GB of it)
