[api] Add getter for EmbedderHeapTracer

Bug: chromium:843903
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I93fffd197d1742d0b00e69e0967a9efb47921208
Reviewed-on: https://chromium-review.googlesource.com/1236253
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56102}

include/v8.h

@@ -7685,6 +7685,11 @@ class V8_EXPORT Isolate {
    */
   void SetEmbedderHeapTracer(EmbedderHeapTracer* tracer);
 
+  /*
+   * Gets the currently active heap tracer for the isolate.
+   */
+  EmbedderHeapTracer* GetEmbedderHeapTracer();
+
   /**
    * Use for |AtomicsWaitCallback| to indicate the type of event it receives.
    */

src/api.cc

@@ -8094,6 +8094,11 @@ void Isolate::SetEmbedderHeapTracer(EmbedderHeapTracer* tracer) {
   isolate->heap()->SetEmbedderHeapTracer(tracer);
 }
 
+EmbedderHeapTracer* Isolate::GetEmbedderHeapTracer() {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  return isolate->heap()->GetEmbedderHeapTracer();
+}
+
 void Isolate::SetGetExternallyAllocatedMemoryInBytesCallback(
     GetExternallyAllocatedMemoryInBytesCallback callback) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);

src/heap/embedder-tracing.h

@@ -24,6 +24,8 @@ class V8_EXPORT_PRIVATE LocalEmbedderHeapTracer final {
     if (remote_tracer_) remote_tracer_->isolate_ = nullptr;
   }
 
+  EmbedderHeapTracer* remote_tracer() const { return remote_tracer_; }
+
   void SetRemoteTracer(EmbedderHeapTracer* tracer) {
     if (remote_tracer_) remote_tracer_->isolate_ = nullptr;
 

src/heap/heap.cc

@@ -4665,6 +4665,10 @@ void Heap::SetEmbedderHeapTracer(EmbedderHeapTracer* tracer) {
   local_embedder_heap_tracer()->SetRemoteTracer(tracer);
 }
 
+EmbedderHeapTracer* Heap::GetEmbedderHeapTracer() const {
+  return local_embedder_heap_tracer()->remote_tracer();
+}
+
 void Heap::TracePossibleWrapper(JSObject* js_object) {
   DCHECK(js_object->IsApiWrapper());
   if (js_object->GetEmbedderFieldCount() >= 2 &&

src/heap/heap.h

@@ -1038,10 +1038,13 @@ class Heap {
   // Embedder heap tracer support. =============================================
   // ===========================================================================
 
-  LocalEmbedderHeapTracer* local_embedder_heap_tracer() {
+  LocalEmbedderHeapTracer* local_embedder_heap_tracer() const {
     return local_embedder_heap_tracer_;
   }
+
   void SetEmbedderHeapTracer(EmbedderHeapTracer* tracer);
+  EmbedderHeapTracer* GetEmbedderHeapTracer() const;
+
   void TracePossibleWrapper(JSObject* js_object);
   void RegisterExternallyReferencedObject(Object** object);
   void SetEmbedderStackStateForNextFinalizaton(