[sapphirecat]

The display always paints from its own top to bottom. Since it has been turned upside down, when you watch really quickly, you can see it painting bottom-to-top from your point of view. This would be true whether the display has Windows rotation or not, and regardless of how apps are writing into the framebuffer.

Windows rotation makes the graphics driver output the framebuffer in reverse, so that the bottom lines of the image appear on the bottom lines of the display from your point of view. This makes the displayed image upright again.

To avoid flicker, Chrome may render offscreen and then copy the result top-to-bottom into the framebuffer. Hence Google's statement that Chrome renders top-to-bottom, and that the screen is displaying bottom-to-top due to rotation.

OK, I think that's enough pedantry for one comment ;)