Tests that time calculator is updated for both visible and hidden requests.
Clicked 'xhr' button.
Appended request [a] of type 'script' is hidden: true from [1] to [2]
Timeline: from [1] to [2]
Appended request [b] of type 'xhr' is hidden: false from [3] to [4]
Timeline: from [1] to [4]
Appended request [c] of type 'script' is hidden: true from [5] to [6]
Timeline: from [1] to [6]