Adding a previews IO-thread blacklist

components/previews/previews_black_list.h

+// 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_PREVIEWS_BLACK_LIST_H_
+#define COMPONENTS_PREVIEWS_PREVIEWS_BLACK_LIST_H_
+
+#include <stdint.h>
+
+#include <memory>
+#include <queue>
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "components/previews/previews_opt_out_store.h"
+
+class GURL;
+
+namespace base {
+class Time;
+}
+
+namespace previews {
+class PreviewsBlackListItem;
+
+// Manages the state of black listed domains for the previews experiment. Loads
+// the stored black list from |opt_out_store| and manages an in memory black
+// list on the IO thread. Updates to the black list are stored in memory and
+// pushed to the store. Asynchronous modifications are stored in a queue and
+// executed in order. Reading from the black list is always synchronous, and if
+// the black list is not currently loaded (e.g., at startup, after clearing
+// browsing history), domains are reported as black listed.
+class PreviewsBlackList {
+ public:
+  // |opt_out_store| is the backing store to retrieve and store black list
+  // information, and can be null. When |opt_out_store| is null, the in-memory
+  // map will be immeadiately loaded to empty. If |opt_out_store| is non-null,
+  // it will be used to load the in-memory map asynchronously.
+  explicit PreviewsBlackList(
+      std::unique_ptr<PreviewsOptOutStore> opt_out_store);
+  ~PreviewsBlackList();
+
+  typedef base::Closure QueueClosure;
+  typedef base::Callback<void(bool)> BlackListedCallback;
+
+  // Asynchronously adds a new navigation to to the in-memory black list and
+  // backing store. |opt_out| is whether the uesr opted out of the preview or
+  // navigated away from the page by another way. |type| is only passed to the
+  // backing store.
+  void AddPreviewNavigation(const GURL& url, bool opt_out, PreviewsType type);
+
+  // Synchronously determines if |host_name| should be allowed to show previews.
+  // If the black list has loaded yet, this will always return false. |type| is
+  // not used to make this decision.
+  bool IsLoadedAndAllowed(const GURL& url, PreviewsType type);
+
+ private:
+  // Synchronously adds a new navigation to the in-memory black list. Adds a new
+  // navigation to backing store. |opt_out| is whether the uesr opted out of

[tbansal1, 2016/09/14 20:17:50]

typo in uesr.

[RyanSturm, 2016/09/14 21:01:04]

Done.

+  // the preview or navigated away from the page by another way. |type| is only

[tbansal1, 2016/09/14 20:17:50]

What is "another way"?

[RyanSturm, 2016/09/14 21:01:04]

Done.

+  // passed to the backing store.
+  void AddPreviewNavigationSync(const GURL& host_name,

[tbansal1, 2016/09/14 20:17:50]

For this function, you can simply say: "Synchronous version of
AddPreviewNavigation method". I do not think there is a need to duplicate
comments.

[RyanSturm, 2016/09/14 21:01:04]

Done.

+                                bool opt_out,
+                                PreviewsType type);
+
+  // Returns the PreviewsBlackListItem representing |host_name|. If there is no
+  // item for |host_name|, one will be created iff |create_if_needed| is true.
+  PreviewsBlackListItem* GetBlackListItem(const std::string& host_name,
+                                          bool create_if_needed);
+
+  // Callback passed to the backing store when loading black list information.
+  // Moves the returned map into the in-memory black list and runs any
+  // outstanding tasks.
+  void LoadBlackListDone(std::unique_ptr<BlackListItemMap> black_list_item_map);
+
+  // Called while waiting for the black list to be loaded from the backing
+  // store.
+  // Enqueues a task to run when when loading black list information has
+  // completed. Maintains the order that tasks were called in.
+  void QueuePendingTask(QueueClosure callback);
+
+  // Map maintaining the in-memory black list.
+  std::unique_ptr<BlackListItemMap> black_list_item_map_;
+
+  // Whether the black list is done being loaded from the backing store.
+  bool loaded_;
+
+  // The backing store of the black list information.
+  std::unique_ptr<PreviewsOptOutStore> opt_out_store_;
+
+  // Callbacks to be run after loading information from the backing store has
+  // completed.
+  std::queue<QueueClosure> pending_callbacks_;
+
+  base::ThreadChecker thread_checker_;
+
+  base::WeakPtrFactory<PreviewsBlackList> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(PreviewsBlackList);
+};
+
+}  // namespace previews
+
+#endif  // COMPONENTS_PREVIEWS_PREVIEWS_BLACK_LIST_ITEM_H_