Turn JSArrayBuffer::flags into a bit field

src/runtime/runtime-typedarray.cc

Index: src/runtime/runtime-typedarray.cc
diff --git a/src/runtime/runtime-typedarray.cc b/src/runtime/runtime-typedarray.cc
index 02b5579bf82715a362a40c87f55d43af6f42e726..c3f69f51508e74683f25ca220e9211f7e5495f2c 100644
--- a/src/runtime/runtime-typedarray.cc
+++ b/src/runtime/runtime-typedarray.cc
@@ -42,7 +42,7 @@ void Runtime::SetupArrayBuffer(Isolate* isolate,
     array_buffer->SetInternalField(i, Smi::FromInt(0));
   }
   array_buffer->set_backing_store(data);
-  array_buffer->set_flag(Smi::FromInt(0));
+  array_buffer->set_bit_field(0);
   array_buffer->set_is_external(is_external);
   array_buffer->set_is_neuterable(true);