Adding a previews IO-thread blacklist

components/previews/core/previews_opt_out_store.h

Index: components/previews/core/previews_opt_out_store.h
diff --git a/components/previews/core/previews_opt_out_store.h b/components/previews/core/previews_opt_out_store.h
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+++ b/components/previews/core/previews_opt_out_store.h
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+// 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.
+
+#ifndef COMPONENTS_PREVIEWS_CORE_PREVIEWS_OPT_OUT_STORE_H_
+#define COMPONENTS_PREVIEWS_CORE_PREVIEWS_OPT_OUT_STORE_H_
+
+#include <stdint.h>
+
+#include <memory>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/time/time.h"
+#include "components/previews/core/previews_black_list_item.h"
+
+class GURL;
+
+namespace previews {
+
+enum class PreviewsType {
+  NONE = 0,
+  OFFLINE = 1,
+  LAST = 2,
+};
+
+typedef std::unordered_map<std::string, std::unique_ptr<PreviewsBlackListItem>>
+    BlackListItemMap;
+
+typedef base::Callback<void(std::unique_ptr<BlackListItemMap>)>
+    LoadBlackListCallback;
+
+// PreviewsOptOutStore keeps opt out information for the previews.
+// Ability to create multiple instances of the store as well as behavior of
+// asynchronous operations when the object is being destroyed, before such
+// operation finishes will depend on implementation. It is possible to issue
+// multiple asynchronous operations in parallel and maintain ordering.
+class PreviewsOptOutStore {
+ public:
+  virtual ~PreviewsOptOutStore() {}
+
+  // Adds a new navigation to the store. |opt_out| is whether the user opted out
+  // of the preview.
+  virtual void AddPreviewNavigation(bool opt_out,
+                                    const std::string& host_name,
+                                    PreviewsType type,
+                                    base::Time now) = 0;
+
+  // Asynchronously loads a map of host names to PreviewsBlackListItem for that
+  // host from the store. And runs |callback| once loading is finished.
+  virtual void LoadBlackList(LoadBlackListCallback callback) = 0;
+};
+
+}  // namespace previews
+
+#endif  // COMPONENTS_PREVIEWS_CORE_PREVIEWS_OPT_OUT_STORE_H_