Extract permission alias info from PermissionsProvider

extensions/common/api_alias_info.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 EXTENSIONS_COMMON_API_ALIAS_INFO_H_
+#define EXTENSIONS_COMMON_API_ALIAS_INFO_H_
+
+#include <vector>
+
+#include "base/lazy_instance.h"
+#include "base/macros.h"
+
+namespace extensions {
+
+class Alias;
+class AliasProvider;
+
+// Global instance containing information about existing API aliases.
+class ApiAliasInfo {

[Devlin, 2016/09/29 22:03:43]

Similarly here, it doesn't look like we use this class at all (beyond
registering providers), so I'd prefer we hold off on its addition.

[tbarzic, 2016/09/29 22:27:13]

I'm working on adding code using this fairly soon (in order of days).

[Devlin, 2016/09/29 22:30:41]

Then let's add it in that CL :)  It's difficult to review code, especially from
an API stand point, when there aren't any uses of it.

[tbarzic, 2016/09/29 22:57:31]

OK, my plan was to reduce the size of that CL, but I think even with moving this
particular part there it should be manageable.

+ public:
+  static ApiAliasInfo* GetInstance();
+
+  // Adds a provider from which additional API aliases are retrieved.
+  // Should be used to initialize |this| - before |api_aliases()| is used.
+  void AddProvider(const AliasProvider& provider);
+
+  const std::vector<Alias>& api_aliases() const { return api_aliases_; }
+
+ private:
+  friend struct base::DefaultLazyInstanceTraits<ApiAliasInfo>;
+
+  ApiAliasInfo();
+  virtual ~ApiAliasInfo();
+
+  // List of known API aliases.
+  std::vector<Alias> api_aliases_;
+
+  DISALLOW_COPY_AND_ASSIGN(ApiAliasInfo);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_COMMON_API_ALIAS_INFO_H_