[api] Add an API function to set the GetExternallyAllocatedMemoryInBytesCallback.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 443353fa78011cd0eb40906ff979f76f4052700c..73f817c6c3a677a1f1b091c2152795db5fd301ca 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -8226,6 +8226,12 @@ void Isolate::SetEmbedderHeapTracer(EmbedderHeapTracer* tracer) {
   isolate->heap()->SetEmbedderHeapTracer(tracer);
 }
 
+void Isolate::SetGetExternallyAllocatedMemoryInBytesCallback(
+    GetExternallyAllocatedMemoryInBytesCallback callback) {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  isolate->heap()->SetGetExternallyAllocatedMemoryInBytesCallback(callback);
+}
+
 void Isolate::TerminateExecution() {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
   isolate->stack_guard()->RequestTerminateExecution();