If the `duration` field passed to performance.measure() is negative, we expect to throw an Exception.
However, due to a typo in PerformanceUserTiming::measure() we actually crash.

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   com.apple.WebCore                   0x000000014e15f23b WTFCrashWithInfo(int, char const*, char const*, int) + 27 (Assertions.h:671)
1   com.apple.WebCore                   0x000000014e219500 std::experimental::fundamentals_v3::__expected_detail::__expected_terminate() + 48 (Expected.h:231)
2   com.apple.WebCore                   0x000000014fab6cd6 std::experimental::fundamentals_v3::expected<double, WebCore::Exception>::error() & + 70 (Expected.h:497)
3   com.apple.WebCore                   0x000000014fab6c21 WebCore::ExceptionOr<double>::releaseException() + 17 (ExceptionOr.h:124)
4   com.apple.WebCore                   0x0000000152a640a9 WebCore::PerformanceUserTiming::measure(JSC::JSGlobalObject&, WTF::String const&, WebCore::PerformanceMeasureOptions const&) + 2057 (PerformanceUserTiming.cpp:214)
5   com.apple.WebCore                   0x0000000152a7d28e WebCore::PerformanceUserTiming::measure(JSC::JSGlobalObject&, WTF::String const&, WTF::Optional<WTF::Variant<WTF::String, WebCore::PerformanceMeasureOptions> >&&, WTF::String const&)::$_1::operator()(WebCore::PerformanceMeasureOptions const&) const + 670 (PerformanceUserTiming.cpp:273)


<rdar://problem/71238176>