Bug was reported by Justin Rogers in:
https://twitter.com/JustRogDigiTec/status/794664508899749888

The repro code is here:

https://jsfiddle.net/tu0muno1/

Basically it just calls performance.now() in one loop, and in another loop calls p.now() where "var p = performance;". Typical results are:

Peformance.now() cached  223.755
Performance.now() not cached  370.04499999999996
Date.now() cached  114.29500000000019
Date.now() not cached  114.21499999999992

So, Performance.now() has worse performance than Date.now(), and it is even worse if 'performance' is not cached in a variable.

Version: 54.0.2840.87 m
OS: The issue exists on both Windows and Linux. However the issue only matters on Windows because the performance of performance.now() and Date.now() on Linux are significantly worse (crbug.com/502205) so the overhead of the non-cached lookup and the extra cost of Performance.now() is a smaller ratio.

Typical Linux results are:
Peformance.now() cached  1667.4150000000002
Performance.now() not cached  1939.0500000000004
Date.now() cached  1442.3200000000006
Date.now() not cached  1456.6800000000003