[Longtasks] Fix frozen value in toJSON() method

Currently, idlharness fails because attribution is not frozen in the
toJSON output. This CL fixes that by calling FreezeV8Object on the
object. In addition to this, we remove the loop and produce interface
objects instead of JSON objects per the algorithm in
https://heycam.github.io/webidl/#es-default-tojson.

Change-Id: Idc4e2adb1c8bfedc296817d1ca259b2ab90fdb21
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1986015
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728222}

third_party/blink/renderer/core/timing/performance_long_task_timing.cc

@@ -43,12 +43,9 @@ TaskAttributionVector PerformanceLongTaskTiming::attribution() const {
 
 void PerformanceLongTaskTiming::BuildJSONValue(V8ObjectBuilder& builder) const {
   PerformanceEntry::BuildJSONValue(builder);
-  HeapVector<ScriptValue> attribution;
-  for (unsigned i = 0; i < attribution_.size(); i++) {
-    attribution.push_back(
-        attribution_[i]->toJSONForBinding(builder.GetScriptState()));
-  }
-  builder.Add("attribution", attribution);
+  ScriptState* script_state = builder.GetScriptState();
+  builder.Add("attribution", FreezeV8Object(ToV8(attribution_, script_state),
+                                            script_state->GetIsolate()));
 }
 
 void PerformanceLongTaskTiming::Trace(blink::Visitor* visitor) {

third_party/blink/web_tests/external/wpt/longtask-timing/idlharness.window-expected.txt

-This is a testharness.js-based test.
-PASS idl_test setup
-PASS idl_test validation
-PASS PerformanceLongTaskTiming interface: existence and properties of interface object
-PASS PerformanceLongTaskTiming interface object length
-PASS PerformanceLongTaskTiming interface object name
-PASS PerformanceLongTaskTiming interface: existence and properties of interface prototype object
-PASS PerformanceLongTaskTiming interface: existence and properties of interface prototype object's "constructor" property
-PASS PerformanceLongTaskTiming interface: existence and properties of interface prototype object's @@unscopables property
-PASS PerformanceLongTaskTiming interface: attribute attribution
-PASS PerformanceLongTaskTiming interface: operation toJSON()
-PASS PerformanceLongTaskTiming must be primary interface of [object PerformanceLongTaskTiming]
-PASS Stringification of [object PerformanceLongTaskTiming]
-PASS PerformanceLongTaskTiming interface: [object PerformanceLongTaskTiming] must inherit property "attribution" with the proper type
-PASS PerformanceLongTaskTiming interface: [object PerformanceLongTaskTiming] must inherit property "toJSON()" with the proper type
-FAIL PerformanceLongTaskTiming interface: default toJSON operation on [object PerformanceLongTaskTiming] assert_true: Value should be frozen expected true got false
-PASS TaskAttributionTiming interface: existence and properties of interface object
-PASS TaskAttributionTiming interface object length
-PASS TaskAttributionTiming interface object name
-PASS TaskAttributionTiming interface: existence and properties of interface prototype object
-PASS TaskAttributionTiming interface: existence and properties of interface prototype object's "constructor" property
-PASS TaskAttributionTiming interface: existence and properties of interface prototype object's @@unscopables property
-PASS TaskAttributionTiming interface: attribute containerType
-PASS TaskAttributionTiming interface: attribute containerSrc
-PASS TaskAttributionTiming interface: attribute containerId
-PASS TaskAttributionTiming interface: attribute containerName
-PASS TaskAttributionTiming interface: operation toJSON()
-PASS TaskAttributionTiming must be primary interface of [object TaskAttributionTiming]
-PASS Stringification of [object TaskAttributionTiming]
-PASS TaskAttributionTiming interface: [object TaskAttributionTiming] must inherit property "containerType" with the proper type
-PASS TaskAttributionTiming interface: [object TaskAttributionTiming] must inherit property "containerSrc" with the proper type
-PASS TaskAttributionTiming interface: [object TaskAttributionTiming] must inherit property "containerId" with the proper type
-PASS TaskAttributionTiming interface: [object TaskAttributionTiming] must inherit property "containerName" with the proper type
-PASS TaskAttributionTiming interface: [object TaskAttributionTiming] must inherit property "toJSON()" with the proper type
-PASS TaskAttributionTiming interface: default toJSON operation on [object TaskAttributionTiming]
-Harness: the test ran to completion.
-