They say at the end of the test they use Safari, but got much better results with Chrome:
"Once our official testing was done, we experimented by conducting the same battery tests using a Chrome browser, rather than Safari. For this exercise, we ran two trials on each of the laptops, and found battery life to be consistently high on all six runs. That’s not enough data for us to draw a conclusion, and in any case a test using Chrome wouldn’t affect our ratings, since we only use the default browser to calculate our scores for all laptops. But it’s something that a MacBook Pro owner might choose to try."
This actually bodes well for battery life once Safari is cleaned up. Safari is a much better energy consumption citizen than Chrome on other Mac laptops, and it's very unlikely something about this new hardware will reverse that relationship.
"Once our official testing was done, we experimented by conducting the same battery tests using a Chrome browser, rather than Safari. For this exercise, we ran two trials on each of the laptops, and found battery life to be consistently high on all six runs. That’s not enough data for us to draw a conclusion, and in any case a test using Chrome wouldn’t affect our ratings, since we only use the default browser to calculate our scores for all laptops. But it’s something that a MacBook Pro owner might choose to try."