This will produce 2 MB of random data and store it in localStorage.
This will reload the browser to a URL that will read a small key from localStorage. For mobile devices, bookmark that URL after clicking this button. Then shut down the browser, and restart the device. Then after restarting, follow that bookmarked link. You may want to engage with the device a little and browse entirely different websites to measure the difference between a cold memory for this origin vs cold state of the device/browser overall.
Navigate back to the neutral URL that doesn't read data.