Tests requests loaded from disk cache have correct timing

URL:http://127.0.0.1:8000/devtools/network/resources/cached-script.php
from memory cache: false
from disk cache: false
has timing: true

URL:http://127.0.0.1:8000/devtools/network/resources/cached-script.php
from memory cache: false
from disk cache: true
has timing: true

Second request starts later than first: true