It is easy to forget to set this flag on macOS, where doing so causes
many tests to fail. So let's just set it via code along with other
options to make it a bit more foolproof.
Useful for finding tests that take a long time to execute.
As of this commit, on macOS, we have:
Text/input/cookie.html: 1228ms
Text/input/css/transition-basics.html: 1060ms
Text/input/HTML/DedicatedWorkerGlobalScope-instanceof.html: 182ms
Text/input/WebAnimations/misc/animation-events-basic.html: 148ms
Text/input/Crypto/SubtleCrypto-deriveBits.html: 130ms
Text/input/IntersectionObserver/observe-box-inside-container-with-scrollable-overflow.html: 117ms
Text/input/navigation/attempt-navigating-object-without-a-document.html: 109ms
Text/input/css/getComputedStyle-print-all.html: 71ms
Text/input/WebAnimations/misc/animation-single-iteration-no-repeat.html: 61ms
Text/input/WebAnimations/animation-methods/updatePlaybackRate.html: 55ms
And on Linux:
Text/input/cookie.html: 1326ms
Text/input/css/transition-basics.html: 1155ms
Screenshot/text-shadow.html: 772ms
Screenshot/css-background-repeat.html: 622ms
Screenshot/object-fit-position.html: 541ms
Screenshot/css-background-position.html: 456ms
Screenshot/css-gradients.html: 451ms
Screenshot/border-radius.html: 400ms
Screenshot/svg-radialGradient.html: 398ms
Text/input/css/getComputedStyle-print-all.html: 325ms
