Merge //content/child/permissions into Blink's permissions module.

content/child/permissions/permission_observers_registry.h

-// Copyright 2015 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 CONTENT_CHILD_PERMISSIONS_PERMISSION_OBSERVERS_REGISTRY_H_
-#define CONTENT_CHILD_PERMISSIONS_PERMISSION_OBSERVERS_REGISTRY_H_
-
-#include <set>
-
-namespace blink {
-class WebPermissionObserver;
-}
-
-namespace content {
-
-// PermissionObserversRegistry keeps a list of WebPermissionObserver with basic
-// methods to add/removed/check. It is being used by PermissionDispatcher and
-// PermissionDispatcherThreadProxy.
-// This is not thread-safe.
-class PermissionObserversRegistry {
- public:
-  PermissionObserversRegistry();
-  ~PermissionObserversRegistry();
-
-  void RegisterObserver(blink::WebPermissionObserver* observer);
-  void UnregisterObserver(blink::WebPermissionObserver* observer);
-  bool IsObserverRegistered(blink::WebPermissionObserver* observer) const;
-
- private:
-  std::set<blink::WebPermissionObserver*> observers_;
-};
-
-}  // namespace content
-
-#endif // CONTENT_CHILD_PERMISSIONS_PERMISSION_OBSERVERS_REGISTRY_H_