Fix a potential crash in const declaration.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 44741fd029f2b9067a48f1e29f5df049cf7fa9d7..ea6ffd8503d785b37ecd654e99ecf0d4cc074340 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -1883,13 +1883,9 @@ void JSObject::LookupCallbackSetterInPrototypes(String* name,
        pt = pt->GetPrototype()) {
     JSObject::cast(pt)->LocalLookupRealNamedProperty(name, result);
     if (result->IsProperty()) {
-      if (result->IsReadOnly()) {
-        result->NotFound();
-        return;
-      }
-      if (result->type() == CALLBACKS) {
-        return;
-      }
+      if (result->type() == CALLBACKS && !result->IsReadOnly()) return;
+      // Found non-callback or read-only callback, stop looking.
+      break;
     }
   }
   result->NotFound();
@@ -2273,10 +2269,10 @@ MUST_USE_RESULT PropertyAttributes JSProxy::GetPropertyAttributeWithHandler(
 
 
 MaybeObject* JSObject::SetPropertyForResult(LookupResult* result,
-                                   String* name,
-                                   Object* value,
-                                   PropertyAttributes attributes,
-                                   StrictModeFlag strict_mode) {
+                                            String* name,
+                                            Object* value,
+                                            PropertyAttributes attributes,
+                                            StrictModeFlag strict_mode) {
   Heap* heap = GetHeap();
   // Make sure that the top context does not change when doing callbacks or
   // interceptor calls.