Add a config class for the settings reset prompt.

chrome/browser/safe_browsing/settings_reset_prompt/settings_reset_prompt_config.h

+// Copyright 2017 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 CHROME_BROWSER_SAFE_BROWSING_SETTINGS_RESET_PROMPT_SETTINGS_RESET_PROMPT_CONFIG_H_
+#define CHROME_BROWSER_SAFE_BROWSING_SETTINGS_RESET_PROMPT_SETTINGS_RESET_PROMPT_CONFIG_H_
+
+#include <cstddef>
+#include <memory>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include "base/feature_list.h"
+#include "base/macros.h"
+
+class GURL;
+
+namespace safe_browsing {
+
+// Exposed for testing.
+extern const base::Feature kSettingsResetPrompt;
+
+// Encapsulates the state of the reset prompt experiment as well as
+// associated data.
+class SettingsResetPromptConfig {
+ public:
+  // Returns true if the settings reset prompt study is enabled.
+  static bool IsPromptEnabled();
+  // Factory method for creating instances of
+  // SettingsResetPromptConfig. Returns nullptr if |IsPromptEnabled()| is
+  // false or if something is wrong with the config parameters.
+  static std::unique_ptr<SettingsResetPromptConfig> Create();
+
+  ~SettingsResetPromptConfig();
+
+  // Returns a non-negative integer ID if |url| should trigger a
+  // settings reset prompt and a negative integer otherwise. The ID is
+  // useful when reporting metrics.

[csharp, 2017/01/09 21:54:59]

Pointer to where the ID mapping for positive values can be found? Or a better
description of what they can mean.

[alito, 2017/01/10 00:37:48]

Added a bit more explanation. However, the mapping of IDs to domains is internal
to the prompt configuration.

+  int UrlToResetDomainId(const GURL& url) const;
+
+  // TODO(alito): parameterize the set of things that we want to reset
+  // for so that we can control it from the finch config. For example,
+  // with functions like HomepageResetAllowed() etc.
+ private:
+  typedef std::vector<uint8_t> SHA256Hash;
+  struct SHA256HashHasher {
+    size_t operator()(const SHA256Hash& key) const;
+  };
+  enum ConfigError : int;
+
+  SettingsResetPromptConfig();
+  bool Init();
+  ConfigError ParseDomainHashes(const std::string& domain_hashes_json);
+
+  // Map of 32 byte SHA256 hashes to integer domain IDs.
+  std::unordered_map<SHA256Hash, int, SHA256HashHasher> domain_hashes_;
+
+  DISALLOW_COPY_AND_ASSIGN(SettingsResetPromptConfig);
+};
+
+}  // namespace safe_browsing.
+
+#endif  // CHROME_BROWSER_SAFE_BROWSING_SETTINGS_RESET_PROMPT_SETTINGS_RESET_PROMPT_CONFIG_H_