lib: predeclare Event.isTrusted property descriptor

[santigimeno]

It improves Event creation performance.

I'm seeing these numbers:

]$ ./node benchmark/compare.js --new ./node --old ./node_old --runs 30 --filter messageport --filter eventtarget worker events  | Rscript benchmark/compare.R
[00:08:18|% 100| 2/2 files | 60/60 runs | 3/3 configs]: Done
                                                                       confidence improvement accuracy (*)   (**)  (***)
events/eventtarget.js listeners=1 n=1000000                                  ***     20.25 %       ±1.64% ±2.18% ±2.85%
events/eventtarget.js listeners=10 n=1000000                                 ***     18.27 %       ±0.88% ±1.18% ±1.53%
events/eventtarget.js listeners=5 n=1000000                                  ***     19.13 %       ±0.96% ±1.29% ±1.71%
worker/messageport.js n=1000000 style='eventemitter' payload='object'                -0.51 %       ±1.85% ±2.46% ±3.20%
worker/messageport.js n=1000000 style='eventemitter' payload='string'                 0.44 %       ±1.12% ±1.49% ±1.94%
worker/messageport.js n=1000000 style='eventtarget' payload='object'         ***      7.18 %       ±1.62% ±2.16% ±2.81%
worker/messageport.js n=1000000 style='eventtarget' payload='string'         ***     10.79 %       ±0.99% ±1.31% ±1.71%

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/49453/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/49455/

[aduh95]

Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1294/

Results

                                                                        confidence improvement accuracy (*)    (**)   (***)
events/ee-add-remove.js n=1000000 removeListener=0 newListener=0                        0.43 %       ±2.53%  ±3.40%  ±4.48%
events/ee-add-remove.js n=1000000 removeListener=0 newListener=1                       -0.11 %       ±1.62%  ±2.16%  ±2.81%
events/ee-add-remove.js n=1000000 removeListener=1 newListener=0                        0.31 %       ±1.17%  ±1.56%  ±2.04%
events/ee-add-remove.js n=1000000 removeListener=1 newListener=1                        0.20 %       ±1.08%  ±1.44%  ±1.87%
events/ee-emit.js listeners=1 argc=0 n=2000000                                         -3.53 %       ±4.02%  ±5.42%  ±7.18%
events/ee-emit.js listeners=1 argc=10 n=2000000                                         1.19 %       ±6.31%  ±8.40% ±10.94%
events/ee-emit.js listeners=1 argc=2 n=2000000                                         -2.07 %       ±4.10%  ±5.52%  ±7.32%
events/ee-emit.js listeners=1 argc=4 n=2000000                                          0.47 %       ±4.73%  ±6.30%  ±8.21%
events/ee-emit.js listeners=10 argc=0 n=2000000                                        -1.08 %       ±3.24%  ±4.31%  ±5.61%
events/ee-emit.js listeners=10 argc=10 n=2000000                                        0.47 %       ±2.89%  ±3.85%  ±5.01%
events/ee-emit.js listeners=10 argc=2 n=2000000                                        -0.26 %       ±2.35%  ±3.12%  ±4.08%
events/ee-emit.js listeners=10 argc=4 n=2000000                                        -1.86 %       ±4.34%  ±5.77%  ±7.52%
events/ee-emit.js listeners=5 argc=0 n=2000000                                          5.84 %       ±7.96% ±10.61% ±13.86%
events/ee-emit.js listeners=5 argc=10 n=2000000                                        -0.10 %       ±5.75%  ±7.65%  ±9.96%
events/ee-emit.js listeners=5 argc=2 n=2000000                                          0.49 %       ±7.78% ±10.35% ±13.47%
events/ee-emit.js listeners=5 argc=4 n=2000000                                         -2.79 %       ±6.36%  ±8.47% ±11.03%
events/ee-listen-unique.js n=1000000 events=1                                           0.55 %       ±1.14%  ±1.52%  ±1.98%
events/ee-listen-unique.js n=1000000 events=10                                          0.76 %       ±1.25%  ±1.67%  ±2.17%
events/ee-listen-unique.js n=1000000 events=2                                           0.35 %       ±0.85%  ±1.13%  ±1.47%
events/ee-listen-unique.js n=1000000 events=20                                         -0.26 %       ±1.77%  ±2.36%  ±3.07%
events/ee-listen-unique.js n=1000000 events=3                                          -1.00 %       ±1.51%  ±2.02%  ±2.65%
events/ee-listen-unique.js n=1000000 events=5                                          -0.72 %       ±1.32%  ±1.77%  ±2.30%
events/ee-listener-count-on-prototype.js n=50000000                                     1.49 %       ±1.94%  ±2.59%  ±3.37%
events/ee-listeners.js raw='false' listeners=5 n=5000000                                0.93 %       ±2.73%  ±3.63%  ±4.73%
events/ee-listeners.js raw='false' listeners=50 n=5000000                              -0.88 %       ±2.66%  ±3.54%  ±4.61%
events/ee-listeners.js raw='true' listeners=5 n=5000000                                -1.96 %       ±7.83% ±10.42% ±13.56%
events/ee-listeners.js raw='true' listeners=50 n=5000000                               -0.46 %       ±2.85%  ±3.79%  ±4.94%
events/ee-once.js argc=0 n=20000000                                                    -0.61 %       ±1.35%  ±1.82%  ±2.39%
events/ee-once.js argc=1 n=20000000                                                     0.38 %       ±0.65%  ±0.86%  ±1.14%
events/ee-once.js argc=4 n=20000000                                                     0.52 %       ±1.72%  ±2.32%  ±3.07%
events/ee-once.js argc=5 n=20000000                                                    -0.73 %       ±1.33%  ±1.77%  ±2.32%
events/eventtarget.js listeners=1 n=1000000                                    ***     19.73 %       ±1.89%  ±2.51%  ±3.27%
events/eventtarget.js listeners=10 n=1000000                                   ***     15.00 %       ±2.71%  ±3.63%  ±4.77%
events/eventtarget.js listeners=5 n=1000000                                    ***     17.72 %       ±2.43%  ±3.24%  ±4.22%
worker/atomics-wait.js n=10000000                                               **     -2.19 %       ±1.58%  ±2.10%  ±2.75%
worker/bench-eventlooputil.js method='ELU_passed' n=1000000                             4.06 %       ±5.00%  ±6.71%  ±8.87%
worker/bench-eventlooputil.js method='ELU_simple' n=1000000                             0.51 %       ±6.67%  ±8.88% ±11.56%
worker/echo.js n=100000 sendsPerBroadcast=1 payload='object' workers=1                 -1.61 %       ±5.24%  ±6.97%  ±9.07%
worker/echo.js n=100000 sendsPerBroadcast=1 payload='string' workers=1                  0.91 %       ±6.01%  ±7.99% ±10.40%
worker/echo.js n=100000 sendsPerBroadcast=10 payload='object' workers=1                -1.56 %       ±3.70%  ±4.92%  ±6.41%
worker/echo.js n=100000 sendsPerBroadcast=10 payload='string' workers=1                -1.37 %       ±3.77%  ±5.04%  ±6.61%
worker/messageport.js n=1000000 style='eventemitter' payload='object'                   0.60 %       ±2.29%  ±3.05%  ±3.98%
worker/messageport.js n=1000000 style='eventemitter' payload='string'                  -0.86 %       ±2.61%  ±3.48%  ±4.53%
worker/messageport.js n=1000000 style='eventtarget' payload='object'           ***      8.44 %       ±3.07%  ±4.08%  ±5.31%
worker/messageport.js n=1000000 style='eventtarget' payload='string'           ***     12.80 %       ±4.71%  ±6.26%  ±8.15%

Be aware that when doing many comparisons the risk of a false-positive
result increases. In this case, there are 45 comparisons, you can thus
expect the following amount of false-positive results:
  2.25 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.45 false positives, when considering a   1% risk acceptance (**, ***),
  0.04 false positives, when considering a 0.1% risk acceptance (***)

[nodejs-github-bot]

Landed in 85c8b78