vm-service: Answer fields from superclass to subclass in declaration order (layout order).

runtime/vm/object_service.cc

Index: runtime/vm/object_service.cc
diff --git a/runtime/vm/object_service.cc b/runtime/vm/object_service.cc
index 90f9e1d67b48d7c170bd2a23efb5103d5c017284..3cfc25b9bbf584d0c739dc36d58b1a328b5ff685 100644
--- a/runtime/vm/object_service.cc
+++ b/runtime/vm/object_service.cc
@@ -1034,27 +1034,34 @@ void Instance::PrintSharedInstanceJSON(JSONObject* jsobj,
     return;
   }
 
-  // Walk the superclass chain, adding all instance fields.
+  // Add all fields in layout order, from superclass to subclass.
+  GrowableArray<Class*> classes;
   Class& cls = Class::Handle(this->clazz());
+  do {
+    cls.Print();
+    classes.Add(&Class::Handle(cls.raw()));
+    cls = cls.SuperClass();
+  } while (!cls.IsNull());
+
+  Array& field_array = Array::Handle();
+  Field& field = Field::Handle();
+  Instance& field_value = Instance::Handle();
   {
-    Instance& fieldValue = Instance::Handle();
     JSONArray jsarr(jsobj, "fields");
-    while (!cls.IsNull()) {
-      const Array& field_array = Array::Handle(cls.fields());
-      Field& field = Field::Handle();
+    for (intptr_t i = classes.length() - 1; i >= 0; i--) {
+      field_array = classes[i]->fields();
       if (!field_array.IsNull()) {
-        for (intptr_t i = 0; i < field_array.Length(); i++) {
-          field ^= field_array.At(i);
+        for (intptr_t j = 0; j < field_array.Length(); j++) {
+          field ^= field_array.At(j);
           if (!field.is_static()) {
-            fieldValue ^= GetField(field);
+            field_value ^= GetField(field);
             JSONObject jsfield(&jsarr);
             jsfield.AddProperty("type", "BoundField");
             jsfield.AddProperty("decl", field);
-            jsfield.AddProperty("value", fieldValue);
+            jsfield.AddProperty("value", field_value);
           }
         }
       }
-      cls = cls.SuperClass();
     }
   }