[runtime] Avoid @@isConcatSpreadable lookup for fast path Array.prototype.concat

test/cctest/heap/test-heap.cc

Index: test/cctest/heap/test-heap.cc
diff --git a/test/cctest/heap/test-heap.cc b/test/cctest/heap/test-heap.cc
index 1ba0f5006a5a7257810ab2472a4939067aa52c22..c15f8063749d040f89aa713cb060bcc99681351c 100644
--- a/test/cctest/heap/test-heap.cc
+++ b/test/cctest/heap/test-heap.cc
@@ -1692,7 +1692,7 @@ int CountNativeContexts() {
   Object* object = CcTest::heap()->native_contexts_list();
   while (!object->IsUndefined()) {
     count++;
-    object = Context::cast(object)->get(Context::NEXT_CONTEXT_LINK);
+    object = Context::cast(object)->next_context_link();
   }
   return count;
 }
@@ -1830,8 +1830,7 @@ static int CountNativeContextsWithGC(Isolate* isolate, int n) {
     count++;
     if (count == n) heap->CollectAllGarbage();
     object =
-        Handle<Object>(Context::cast(*object)->get(Context::NEXT_CONTEXT_LINK),
-                       isolate);
+        Handle<Object>(Context::cast(*object)->next_context_link(), isolate);
   }
   return count;
 }