Use proper write barrier mode when creating rest parameters.

BUG=chromium:623912

Review-Url: https://codereview.chromium.org/2109603002
Cr-Commit-Position: refs/heads/master@{#37326}

src/runtime/runtime-scopes.cc

@@ -558,7 +558,7 @@ RUNTIME_FUNCTION(Runtime_NewRestParameter) {
   {
     DisallowHeapAllocation no_gc;
     FixedArray* elements = FixedArray::cast(result->elements());
-    WriteBarrierMode mode = result->GetWriteBarrierMode(no_gc);
+    WriteBarrierMode mode = elements->GetWriteBarrierMode(no_gc);
     for (int i = 0; i < num_elements; i++) {
       elements->set(i, *arguments[i + start_index], mode);
     }