Keep track of array buffers in new space separately

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 4f16120df33ddbb4d096c4a3a33820b911986833..c422a12e2a1f819f2878d4bb789fd41d56084317 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -6259,7 +6259,8 @@ v8::ArrayBuffer::Contents v8::ArrayBuffer::Externalize() {
   Utils::ApiCheck(!self->is_external(), "v8::ArrayBuffer::Externalize",
                   "ArrayBuffer already externalized");
   self->set_is_external(true);
-  isolate->heap()->UnregisterArrayBuffer(self->backing_store());
+  isolate->heap()->UnregisterArrayBuffer(isolate->heap()->InNewSpace(*self),
+                                         self->backing_store());
 
   return GetContents();
 }