feat(ext/web): add performance.toJSON (#14548)

cli/dts/lib.deno.shared_globals.d.ts

@@ -450,6 +450,7 @@ declare class Worker extends EventTarget {
 declare type PerformanceEntryList = PerformanceEntry[];
 
 declare class Performance {
+  /** Returns a timestamp representing the start of the performance measurement. */
   readonly timeOrigin: number;
   constructor();
 
@@ -490,6 +491,9 @@ declare class Performance {
    * ```
    */
   now(): number;
+
+  /** Returns a JSON representation of the performance object. */
+  toJSON(): any;
 }
 
 declare var performance: Performance;

cli/tests/unit/performance_test.ts

@@ -27,6 +27,15 @@ Deno.test(function timeOrigin() {
   assert(Date.now() >= origin);
 });
 
+Deno.test(function performanceToJSON() {
+  const json = performance.toJSON();
+
+  assert("timeOrigin" in json);
+  assert(json.timeOrigin === performance.timeOrigin);
+  // check there are no other keys
+  assertEquals(Object.keys(json).length, 1);
+});
+
 Deno.test(function performanceMark() {
   const mark = performance.mark("test");
   assert(mark instanceof PerformanceMark);

ext/web/15_performance.js

@@ -556,7 +556,9 @@
 
     toJSON() {
       webidl.assertBranded(this, PerformancePrototype);
-      return {};
+      return {
+        timeOrigin: this.timeOrigin,
+      };
     }
 
     [customInspect](inspect) {

tools/wpt/expectation.json

@@ -1182,13 +1182,11 @@
     "idlharness.any.html": [
       "Performance interface: existence and properties of interface object",
       "Performance interface: existence and properties of interface prototype object",
-      "Performance interface: default toJSON operation on performance",
       "Window interface: attribute performance"
     ],
     "idlharness.any.worker.html": [
       "Performance interface: existence and properties of interface object",
       "Performance interface: existence and properties of interface prototype object",
-      "Performance interface: default toJSON operation on performance",
       "WorkerGlobalScope interface: attribute performance",
       "WorkerGlobalScope interface: self must inherit property \"performance\" with the proper type"
     ],