lib: use class fields in observe.js

https://bugs.chromium.org/p/v8/issues/detail?id=10704 is already
fixed, so switch back to class fields instead of using
symbol properties.

PR-URL: #42361
Refs: b1c3909
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Mestery <mestery@protonmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>

Author: joyeecheung

lib/internal/perf/observe.js

@@ -61,13 +61,9 @@ const {
 
 const { inspect } = require('util');
 
-const kBuffer = Symbol('kBuffer');
-const kCallback = Symbol('kCallback');
 const kDispatch = Symbol('kDispatch');
-const kEntryTypes = Symbol('kEntryTypes');
 const kMaybeBuffer = Symbol('kMaybeBuffer');
 const kDeprecatedFields = Symbol('kDeprecatedFields');
-const kType = Symbol('kType');
 
 const kDeprecationMessage =
   'Custom PerformanceEntry accessors are deprecated. ' +
@@ -151,32 +147,34 @@ function maybeIncrementObserverCount(type) {
 }
 
 class PerformanceObserverEntryList {
+  #buffer = [];
+
   constructor(entries) {
-    this[kBuffer] = ArrayPrototypeSort(entries, (first, second) => {
+    this.#buffer = ArrayPrototypeSort(entries, (first, second) => {
       return first.startTime - second.startTime;
     });
   }
 
   getEntries() {
-    return ArrayPrototypeSlice(this[kBuffer]);
+    return ArrayPrototypeSlice(this.#buffer);
   }
 
   getEntriesByType(type) {
     type = `${type}`;
     return ArrayPrototypeFilter(
-      this[kBuffer],
+      this.#buffer,
       (entry) => entry.entryType === type);
   }
 
   getEntriesByName(name, type) {
     name = `${name}`;
     if (type != null /** not nullish */) {
       return ArrayPrototypeFilter(
-        this[kBuffer],
+        this.#buffer,
         (entry) => entry.name === name && entry.entryType === type);
     }
     return ArrayPrototypeFilter(
-      this[kBuffer],
+      this.#buffer,
       (entry) => entry.name === name);
   }
 
@@ -188,20 +186,19 @@ class PerformanceObserverEntryList {
       depth: options.depth == null ? null : options.depth - 1
     };
 
-    return `PerformanceObserverEntryList ${inspect(this[kBuffer], opts)}`;
+    return `PerformanceObserverEntryList ${inspect(this.#buffer, opts)}`;
   }
 }
 
 class PerformanceObserver {
+  #buffer = [];
+  #entryTypes = new SafeSet();
+  #type;
+  #callback;
+
   constructor(callback) {
-    // TODO(joyeecheung): V8 snapshot does not support instance member
-    // initializers for now:
-    // https://bugs.chromium.org/p/v8/issues/detail?id=10704
-    this[kBuffer] = [];
-    this[kEntryTypes] = new SafeSet();
-    this[kType] = undefined;
     validateFunction(callback, 'callback');
-    this[kCallback] = callback;
+    this.#callback = callback;
   }
 
   observe(options = {}) {
@@ -219,10 +216,10 @@ class PerformanceObserver {
                                       'options.entryTypes can not set with ' +
                                       'options.type together');
 
-    switch (this[kType]) {
+    switch (this.#type) {
       case undefined:
-        if (entryTypes !== undefined) this[kType] = kTypeMultiple;
-        if (type !== undefined) this[kType] = kTypeSingle;
+        if (entryTypes !== undefined) this.#type = kTypeMultiple;
+        if (type !== undefined) this.#type = kTypeSingle;
         break;
       case kTypeSingle:
         if (entryTypes !== undefined)
@@ -238,53 +235,53 @@ class PerformanceObserver {
         break;
     }
 
-    if (this[kType] === kTypeMultiple) {
+    if (this.#type === kTypeMultiple) {
       if (!ArrayIsArray(entryTypes)) {
         throw new ERR_INVALID_ARG_TYPE(
           'options.entryTypes',
           'string[]',
           entryTypes);
       }
-      maybeDecrementObserverCounts(this[kEntryTypes]);
-      this[kEntryTypes].clear();
+      maybeDecrementObserverCounts(this.#entryTypes);
+      this.#entryTypes.clear();
       for (let n = 0; n < entryTypes.length; n++) {
         if (ArrayPrototypeIncludes(kSupportedEntryTypes, entryTypes[n])) {
-          this[kEntryTypes].add(entryTypes[n]);
+          this.#entryTypes.add(entryTypes[n]);
           maybeIncrementObserverCount(entryTypes[n]);
         }
       }
     } else {
       if (!ArrayPrototypeIncludes(kSupportedEntryTypes, type))
         return;
-      this[kEntryTypes].add(type);
+      this.#entryTypes.add(type);
       maybeIncrementObserverCount(type);
       if (buffered) {
         const entries = filterBufferMapByNameAndType(undefined, type);
-        ArrayPrototypePushApply(this[kBuffer], entries);
+        ArrayPrototypePushApply(this.#buffer, entries);
         kPending.add(this);
         if (kPending.size)
           queuePending();
       }
     }
 
-    if (this[kEntryTypes].size)
+    if (this.#entryTypes.size)
       kObservers.add(this);
     else
       this.disconnect();
   }
 
   disconnect() {
-    maybeDecrementObserverCounts(this[kEntryTypes]);
+    maybeDecrementObserverCounts(this.#entryTypes);
     kObservers.delete(this);
     kPending.delete(this);
-    this[kBuffer] = [];
-    this[kEntryTypes].clear();
-    this[kType] = undefined;
+    this.#buffer = [];
+    this.#entryTypes.clear();
+    this.#type = undefined;
   }
 
   takeRecords() {
-    const list = this[kBuffer];
-    this[kBuffer] = [];
+    const list = this.#buffer;
+    this.#buffer = [];
     return list;
   }
 
@@ -293,17 +290,17 @@ class PerformanceObserver {
   }
 
   [kMaybeBuffer](entry) {
-    if (!this[kEntryTypes].has(entry.entryType))
+    if (!this.#entryTypes.has(entry.entryType))
       return;
-    ArrayPrototypePush(this[kBuffer], entry);
+    ArrayPrototypePush(this.#buffer, entry);
     kPending.add(this);
     if (kPending.size)
       queuePending();
   }
 
   [kDispatch]() {
-    this[kCallback](new PerformanceObserverEntryList(this.takeRecords()),
-                    this);
+    this.#callback(new PerformanceObserverEntryList(this.takeRecords()),
+                   this);
   }
 
   [kInspect](depth, options) {
@@ -317,8 +314,8 @@ class PerformanceObserver {
     return `PerformanceObserver ${inspect({
       connected: kObservers.has(this),
       pending: kPending.has(this),
-      entryTypes: ArrayFrom(this[kEntryTypes]),
-      buffer: this[kBuffer],
+      entryTypes: ArrayFrom(this.#entryTypes),
+      buffer: this.#buffer,
     }, opts)}`;
   }
 }