cppgc: Fix leftover cached events

Clear cached events if there is no embedder recorder.

Bug: chromium:1154636
Change-Id: I9ad3b752ea242d07b417ce3022936789c47afc6a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3358292Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78464}

src/heap/cppgc-js/cpp-heap.cc

@@ -233,6 +233,7 @@ void UnifiedHeapMarker::AddObject(void* object) {
 
 void CppHeap::MetricRecorderAdapter::AddMainThreadEvent(
     const FullCycle& cppgc_event) {
+  DCHECK(!last_full_gc_event_.has_value());
   last_full_gc_event_ = cppgc_event;
   GetIsolate()->heap()->tracer()->NotifyGCCompleted();
 }
@@ -311,6 +312,13 @@ CppHeap::MetricRecorderAdapter::ExtractLastIncrementalMarkEvent() {
   return std::move(last_incremental_mark_event_);
 }
 
+void CppHeap::MetricRecorderAdapter::ClearCachedEvents() {
+  incremental_mark_batched_events_.events.clear();
+  incremental_sweep_batched_events_.events.clear();
+  last_incremental_mark_event_.reset();
+  last_full_gc_event_.reset();
+}
+
 Isolate* CppHeap::MetricRecorderAdapter::GetIsolate() const {
   DCHECK_NOT_NULL(cpp_heap_.isolate());
   return reinterpret_cast<Isolate*>(cpp_heap_.isolate());

src/heap/cppgc-js/cpp-heap.h

@@ -64,6 +64,8 @@ class V8_EXPORT_PRIVATE CppHeap final
         cppgc::internal::MetricRecorder::MainThreadIncrementalMark>
     ExtractLastIncrementalMarkEvent();
 
+    void ClearCachedEvents();
+
    private:
     Isolate* GetIsolate() const;
 

src/heap/gc-tracer.cc

@@ -1381,7 +1381,16 @@ void GCTracer::ReportFullCycleToRecorder() {
   const std::shared_ptr<metrics::Recorder>& recorder =
       heap_->isolate()->metrics_recorder();
   DCHECK_NOT_NULL(recorder);
-  if (!recorder->HasEmbedderRecorder()) return;
+  metrics_report_pending_ = false;
+  if (!recorder->HasEmbedderRecorder()) {
+    incremental_mark_batched_events_.events.clear();
+    if (heap_->cpp_heap()) {
+      v8::internal::CppHeap::From(heap_->cpp_heap())
+          ->GetMetricRecorder()
+          ->ClearCachedEvents();
+    }
+    return;
+  }
   if (!incremental_mark_batched_events_.events.empty()) {
     FlushBatchedIncrementalEvents(incremental_mark_batched_events_,
                                   heap_->isolate());
@@ -1416,7 +1425,6 @@ void GCTracer::ReportFullCycleToRecorder() {
   }
   // TODO(chromium:1154636): Populate v8 metrics.
   recorder->AddMainThreadEvent(event, GetContextId(heap_->isolate()));
-  metrics_report_pending_ = false;
 }
 
 void GCTracer::ReportIncrementalMarkingStepToRecorder() {