perf(proxy): Use per‑class Proxy handler

[ExE-Boss]

Currently, a new Proxy handler is created per‑instance, this is inefficient and unnecessary, especially since the proxy handlers don’t depend on any instance‑specific state.

[domenic]

Can you show before/after benchmarks to demonstrate a perf improvement?

[TimothyGu]

This looks good but I'd also be interested in seeing benchmark results, especially in terms of memory usage. I.e., how much memory does an additional handler with its own copy of handler methods actually take?

[ExE-Boss]

There’s a decent performance increase with this:

benchmark	per‑instance Proxy handler	per‑class Proxy handler
dom/compare-document-position/compare ancestor	jsdom × 33,877 ops/sec ±2.88% (14 runs sampled)	jsdom × 35,270 ops/sec ±2.83% (15 runs sampled)
dom/compare-document-position/compare descendant	jsdom × 34,320 ops/sec ±2.22% (14 runs sampled)	jsdom × 34,349 ops/sec ±4.54% (14 runs sampled)
dom/compare-document-position/compare siblings	jsdom × 1,316,711 ops/sec ±3.36% (9 runs sampled)	jsdom × 1,407,317 ops/sec ±1.92% (12 runs sampled)
dom/construction/createComment	jsdom × 1,235,394 ops/sec ±4.44% (92 runs sampled)	jsdom × 1,248,180 ops/sec ±2.31% (89 runs sampled)
dom/construction/createDocumentFragment	jsdom × 1,270,944 ops/sec ±0.41% (97 runs sampled)	jsdom × 1,288,443 ops/sec ±0.44% (98 runs sampled)
dom/construction/createElement	jsdom × 221,507 ops/sec ±2.86% (87 runs sampled)	jsdom × 324,510 ops/sec ±0.39% (98 runs sampled)
dom/construction/createEvent	jsdom × 191,764 ops/sec ±1.94% (92 runs sampled)	jsdom × 193,381 ops/sec ±1.78% (89 runs sampled)
dom/construction/createNodeIterator	jsdom × 1,247,649 ops/sec ±0.28% (94 runs sampled)	jsdom × 1,274,109 ops/sec ±0.41% (98 runs sampled)
dom/construction/createProcessingInstruction	jsdom × 627,401 ops/sec ±0.32% (95 runs sampled)	jsdom × 633,693 ops/sec ±0.38% (95 runs sampled)
dom/construction/createTextNode	jsdom × 973,704 ops/sec ±0.49% (99 runs sampled)	jsdom × 999,581 ops/sec ±2.17% (90 runs sampled)
dom/inner-html/tables	jsdom × 0.33 ops/sec ±1.98% (5 runs sampled)	jsdom × 0.36 ops/sec ±3.74% (5 runs sampled)
dom/named-properties/setAttribute(): Remove a named property from window	jsdom × 2,904 ops/sec ±4.53% (56 runs sampled)	jsdom × 3,488 ops/sec ±0.94% (61 runs sampled)
dom/tree-modification/appendChild: many parents	jsdom × 28.77 ops/sec ±0.84% (49 runs sampled)	jsdom × 30.67 ops/sec ±0.80% (52 runs sampled)
dom/tree-modification/appendChild: many siblings	jsdom × 245,236 ops/sec ±13.16% (16 runs sampled)	jsdom × 270,620 ops/sec ±10.80% (17 runs sampled)
dom/tree-modification/appendChild: no siblings	jsdom × 217,962 ops/sec ±11.74% (21 runs sampled)	jsdom × 261,350 ops/sec ±6.80% (25 runs sampled)
dom/tree-modification/insertBefore: many siblings	jsdom × 236,425 ops/sec ±12.12% (15 runs sampled)	jsdom × 269,569 ops/sec ±1.72% (18 runs sampled)
dom/tree-modification/removeChild: many parents	jsdom × 122 ops/sec ±1.07% (64 runs sampled)	jsdom × 130 ops/sec ±0.77% (63 runs sampled)
dom/tree-modification/removeChild: many siblings	jsdom × 133,626 ops/sec ±7.42% (35 runs sampled)	jsdom × 149,070 ops/sec ±7.08% (38 runs sampled)
dom/tree-modification/removeChild: no siblings	jsdom × 118,199 ops/sec ±11.44% (23 runs sampled)	jsdom × 136,483 ops/sec ±10.06% (30 runs sampled)
html/parsing/text	jsdom × 14.23 ops/sec ±1.51% (40 runs sampled)	jsdom × 14.34 ops/sec ±1.82% (41 runs sampled)
jsdom/api/new JSDOM() defaults	<Test #⁠10> × 261 ops/sec ±4.49% (73 runs sampled)	<Test #⁠10> × 303 ops/sec ±4.44% (77 runs sampled)
jsdom/api/new JSDOM() with many elements	<Test #⁠11> × 27.18 ops/sec ±14.82% (51 runs sampled)	<Test #⁠11> × 33.18 ops/sec ±4.74% (60 runs sampled)

[domenic]

Nice. In that case let's merge this.