          // 0.
          assert_positive_(
            frame.contentWindow.performance.getEntriesByType('resource')
              .filter(e => e.name.includes(url))[0], ['transferSize']);

          // Load the same script onto the parent document. This time the script
          // is coming from memory cache.
          return getScript(url);
        })
        .then(() => {
          // Verify that the transferSize in case of memory cache load is 0.
          assert_zeroed_(
            window.performance