Adding a previews IO-thread blacklist

components/previews/core/previews_opt_out_store.cc

Index: components/previews/core/previews_opt_out_store.cc
diff --git a/components/previews/core/previews_opt_out_store.cc b/components/previews/core/previews_opt_out_store.cc
new file mode 100644
index 0000000000000000000000000000000000000000..231755c0c1861bbb91270d859e9b49282df3f146
--- /dev/null
+++ b/components/previews/core/previews_opt_out_store.cc
@@ -0,0 +1,13 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/previews/core/previews_opt_out_store.h"
+
+namespace previews {
+
+PreviewsOptOutStore::PreviewsOptOutStore() {}
+
+PreviewsOptOutStore::~PreviewsOptOutStore() {}
+
+}  // namespace previews